Aqueous polymer dispersions and products from those dispersions

ABSTRACT

A method for forming a heat sealable coating on a substrate, wherein the substrate is formed from at least one oriented polymer is shown. The method includes depositing an aqueous polymer dispersion on the substrate, wherein the aqueous polymer dispersion includes (A) at least one thermoplastic resin; (B) at least one dispersing agent; and (C) water; wherein the dispersion has a pH of less than 12, and drying the dispersion to form a first layer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application is a continuation of U.S. patent applicationSer. No. 12/815,918, filed on Jun. 15, 2010, which is a divisionalapplication of U.S. patent application Ser. No. 11/068,573, which claimsthe benefit, pursuant to 35 U.S.C. §120 as a continuation in partapplication of U.S. patent application Ser. No. 10/925,693, which claimspriority to U.S. Provisional Application Ser. No. 60/497,527, filed onAug. 25, 2003, and U.S. Provisional Application Ser. No. 60/548,493,filed on Feb. 27, 2004, the teachings of which are incorporated byreference herein, as if reproduced in full hereinbelow.

BACKGROUND OF INVENTION

Aqueous dispersions of a thermoplastic resin of various types are knownin the art. Aqueous dispersions have been used in a wide variety offields since an aqueous dispersion prepared by using water as itsdispersion medium is far more advantageous than the dispersions preparedby using an organic solvent for the dispersion medium in view offlammability, working environment, handling convenience, and the like.For example, when an aqueous dispersion is coated and dried on a surfaceof a substrate such as paper, fiber, wood, metal, or plastic moldedarticle, the resin coating formed will provide the substrate with waterresistance, oil resistance, chemical resistance, corrosion resistanceand heat sealability.

Conventional aqueous dispersions of a thermoplastic resin have beenproduced either by a process wherein a polymerizable monomer which isthe resin raw material is polymerized by emulsion polymerization in anaqueous medium in the presence of a dispersing agent, or by a processwherein a molten thermoplastic resin and an aqueous medium, andoptionally, a dispersing agent are mixed by applying shearing force. Theformer process is associated with the disadvantage of the limited numberof the polymerizable monomers that can be used, and hence, the varietyof the aqueous dispersions of the thermoplastic resin that can beproduced, is limited. The former process also suffers from complicatedcontrol of the polymerization reaction as well as intricate equipment.On the other hand, the latter process is applicable to a wide variety ofresins in relatively simple equipment.

One particular application for coatings made from dispersions is inpackaging and storage container applications. To be useful, a balance ofperformance properties such as low heat seal initiation temperature, ahigh hot tack strength, a broad hot sealing window, good interlayeradhesion, and a high softening point is desirable.

The commercial importance of balanced sealant properties is wellunderstood. That is, low heat seal initiation temperatures are importantfor improved sealing speeds and reduced energy utilization. A broadsealing window is important for insuring package integrity, sealingequipment flexibility and low package leakage rates.

Good interlayer adhesion is also important for good package integrity aswell as good package or container aesthetics. High softening points ortemperatures are desired where goods are packaged at elevatedtemperatures such as in hot-fill applications. Traditionally, whenattempting to achieve balanced sealant properties, enhancement of oneparticular resin property has required some sacrifice with respect toanother important property.

For instance, with ethylene alpha-olefin polymers, low heat sealinitiation temperatures are typically achieved by increasing thecomonomer content of the resin. Conversely, high Vicat softening pointsand low levels of n-hexane extractives are typically achieved bydecreasing the comonomer content of the resin. Accordingly, lowering theheat seal initiation temperature typically results in proportionallyreduced Vicat softening temperature and proportionally increasedextractable level. U.S. Pat. No. 5,874,139, which is assigned to theassignee of the present invention and is expressly incorporated byreference in its entirety, provides a general discussion of polyolefinsin packaging applications.

Several important multilayer packaging and storage structures consist ofa polypropylene layer, particularly, a biaxially oriented polypropylenehomopolymer (BOPP) base or core layer. Often, BOPP structures utilizepolypropylene copolymers and terpolymers as sealant materials (and/oradhesive layers) to insure good interlayer adhesion to the BOPP baselayer. While polypropylene copolymers and terpolymers do indeed providegood interlayer adhesion to BOPP base layers as well as good heat sealstrength performance, these copolymers and terpolymers sometimes exhibitundesirably high heat seal initiation temperatures.

Other materials have also been used as sealant materials for multilayerpackaging and storage structures. However, in general, known sealantmaterials do not provide the desired overall property balance and/orprocess flexibility desired by converters and packagers.

SUMMARY OF INVENTION

In one aspect the invention provides an aqueous dispersion comprising(A) at least one thermoplastic resin; (B) at least one dispersing agent;and (C) water; wherein the dispersion has a pH of less than 12. Inanother aspect the invention provides an aqueous dispersion comprising(A) at least one thermoplastic resin; (B) at least one dispersing agent;and (C) water wherein the dispersion has a volume average particle sizeof less than about 5 μm. In some dispersions according to either aspect,the dispersing agent comprises less than about 4 percent by weight basedon the weight of the thermoplastic resin. In some dispersions having apH of 12 or less, the dispersion also has a volume average particle sizeof less than about 5 μm. Some dispersions that have a particle size ofless than about 5 μm also have a pH of less than 12. In still otherembodiments, the dispersion has a pH of less than 12, and an averageparticle size of less than about 5 μm, and wherein the dispersing agentcomprises less than about 4 percent by weight based on the weight of thethermoplastic resin.

In some dispersions the thermoplastic resin is an alpha-olefininterpolymer of ethylene with at least one comonomer selected from thegroup consisting of a C₄-C₂₀ linear, branched or cyclic diene, or anethylene vinyl compound, such as vinyl acetate, and a compoundrepresented by the formula H₂C═CHR wherein R is a C₁-C₂₀ linear,branched or cyclic alkyl group or a C6-C₂₀ aryl group. Preferredcomonomers include propylene, 1-butene, 3-methyl-1-butene,4-methyl-1-pentene, 3-methyl-1-pentene, 1-heptene, 1-hexene, 1-octene,1-decene, and 1-dodecene. In some embodiments, the interpolymer ofethylene has a density of less than about 0.92 g/cc.

In other embodiments, the thermoplastic resin comprises an alpha-olefininterpolymer of propylene with at least one comonomer selected from thegroup consisting of ethylene, a C₄-C₂₀ linear, branched or cyclic diene,and a compound represented by the formula H₂C═CHR wherein R is a C₁-C₂₀linear, branched or cyclic alkyl group or a C₆-C₂₀ aryl group. Preferredcomonomers include ethylene, 1-butene, 3-methyl-1-butene,4-methyl-1-pentene, 3-methyl-1-pentene, 1-heptene, 1-hexene, 1-octene,1-decene, and 1-dodecene. In some embodiments, the comonomer is presentat about 5% by weight to about 25% by weight of the interpolymer. Insome embodiments, a propylene-ethylene interpolymer is preferred.

Some interpolymers of propylene that are useful in particularembodiments are propylene-rich alpha-olefin interpolymer comprising 5 to25% by weight of ethylene-derived units and 95 to 75% by weight ofpropylene-derived units. In some embodiments, propylene richalpha-olefin interpolymers having (a) a melting point of less than 90°C.; a relationship of elasticity to 500% tensile modulus such that theelasticity is less than or equal to 0.935M+12, where elasticity is inpercent and M is the 500% tensile modulus in MPa; and a relationship offlexural modulus to 500% tensile modulus such that flexural modulus isless than or equal to 4.2e^(0.27M)+50, where flexural modulus is in MPaand M is the 500% tensile modulus in MPa are preferred. In someembodiments, the propylene rich alpha-olefin interpolymer comprises 6 to20% by weight of ethylene-derived units and 94 to 80% by weight ofpropylene-derived units. In other embodiments, polymers comprising 8 to20% by weight of ethylene-derived units and 92 to 80% by weight ofpropylene-derived units are preferred. In still other embodiments,polymers comprising 10 to 20% by weight of ethylene-derived units and 90to 80% by weight of propylene-derived units.

In other embodiments, a propylene-rich alpha-olefin interpolymer thatcomprises a copolymer of propylene and at least one comonomer selectedfrom the group consisting of ethylene and C₄ to C₂₀ alpha-olefins,wherein the copolymer has a propylene content of greater than 65 molepercent, a weight average molecular weight (Mw) of from about 15,000 toabout 200,000, a weight average molecular weight/number averagemolecular weight ratio (Mw/Mn) of from about 1.5 to about 4 ispreferred.

Some propylene-rich alpha-olefin interpolymers have a heat of fusion ofless than about 80 J/g, preferably from about 8 to about 80, or fromabout 8 to about 30 J/g as determined by DSC.

In some embodiments, the at least one thermoplastic resin has acrystallinity of less than about 50%. In other embodiments, thecrystallinity ranges from about 5% to about 45%, or from about 5% toabout 40%.

Any suitable dispersing agent can be used. However, in particularembodiments, the dispersing agent comprises at least one carboxylicacid, a salt of at least one carboxylic acid, or carboxylic acid esteror salt of the carboxylic acid ester. One example of a carboxylic aciduseful as a dispersant is a fatty acid such as montanic acid. In somepreferred embodiments, the carboxylic acid, the salt of the carboxylicacid, or at least one carboxylic acid fragment of the carboxylic acidester or at least one carboxylic acid fragment of the salt of thecarboxylic acid ester has fewer than 25 carbon atoms. In otherembodiments, the carboxylic acid, the salt of the carboxylic acid, or atleast one carboxylic acid fragment of the carboxylic acid ester or atleast one carboxylic acid fragment of the salt of the carboxylic acidester has 12 to 25 carbon atoms. In some embodiments, carboxylic acids,salts of the carboxylic acid, at least one carboxylic acid fragment ofthe carboxylic acid ester or its salt has 15 to 25 carbon atoms arepreferred. In other embodiments, the number of carbon atoms is 25 to 60.Some preferred salts comprise a cation selected from the groupconsisting of an alkali metal cation, alkaline earth metal cation, orammonium or alkyl ammonium cation.

In still other embodiments, the dispersing agent is selected from thegroup consisting of ethylene carboxylic acid polymers, and their salts,such as ethylene acrylic acid copolymers or ethylene methacrylic acidcopolymers.

In other embodiments, the dispersing agent is selected from alkyl ethercarboxylates, petroleum sulfonates, sulfonated polyoxyethylenatedalcohol, sulfated or phosphated polyoxyethylenated alcohols, polymericethylene oxide/propylene oxide/ethylene oxide dispersing agents, primaryand secondary alcohol ethoxylates, alkyl glycosides and alkylglycerides.

Combinations of any of the above-enumerated dispersing agents can alsobe used to prepared some aqueous dispersions.

Some dispersions described herein have an advantageous particle sizedistribution. In particular embodiments, the dispersion has a particlesize distribution defined as volume average particle diameter (Dv)divided by number average particle diameter (Dn) of less than or equalto about 2.0. In other embodiments, the dispersion has a particle sizedistribution of less than or equal to about 1.5.

Some dispersions described herein comprise particles having an averageparticle size of less than about 1.5 μm. In other embodiments, theaverage particle size ranges from about 0.05 μm to about 1.5 μm. Instill other embodiments, the average particle size of the dispersionranges from about 0.5 μm to about 1.5 μm.

For dispersions having a pH of less than 12, some dispersions have a pHof from about 5 to about 11.5, preferably from about 7 to about 11, morepreferably from about 9 to about 11. The pH can be controlled by anumber of factors, including type or strength of base (dispersingagent), degree of conversion of the base to the salt form, type ofthermoplastic polymer to be dispersed, and melt kneading (e.g.,extruder) processing conditions. The pH can be adjusted either in-situ,or by converting the carboxylic acid dispersing agent to the salt formbefore adding it to the thermoplastic resin and forming the dispersion.Of these, forming the salt in-situ is preferred.

Preferably, the dispersions are characterized by a percent solidscontent of less than about 74% by volume. Some dispersions have apercent solids of from about 5% to about 74% by volume. Still otherdispersions have a percent solids of less than about 70% by volume, lessthan about 65% by volume, or from about 5% to about 50% by volume.

In another aspect, embodiments of the invention provide a method forproducing an aqueous dispersion comprising: (1) melt kneading (A) atleast one thermoplastic resin and (B) at least one dispersing agent, toproduce a melt-kneaded product and (2) diluting said melt-kneadedproduct, and melt kneading the resulting mixture to form the aqueousdispersion, wherein the dispersion has an average particle size of lessthan about 5 μm. Other embodiments provide a method for producing anaqueous dispersion comprising: (1) melt kneading (A) at least onethermoplastic resin, and (B) at least one dispersing agent, to produce amelt-kneaded product, and (2) diluting said melt-kneaded product, andmelt kneading the resulting mixture to form the aqueous dispersion toproduce a dispersion having a pH of less than 12. In some methodsaccording to either aspect, the dispersing agent comprises less thanabout 4 percent by weight based on the weight of the thermoplasticresin. In some methods that provide a dispersion having a pH of 12 orless, the dispersion also has a volume average particle size of lessthan about 5 μm. Some dispersions that have a particle size of less thanabout 5 μm also have a pH of less than 12. Embodiments of the methodsuse the thermoplastic resins and dispersing agents described above. Andin some embodiments, the methods provide dispersions having one or moreof the properties described above.

In another aspect, embodiments of the invention provide an aqueousdispersion comprising (A) at least one propylene-rich alpha-olefininterpolymer; (B) at least one dispersing agent; and (C) water. Onpreferred alpha-olefin is ethylene, preferably present in an amount offrom about 5% to about 25% by weight. In some embodiments of theinvention according to this aspect the propylene-rich alpha-olefininterpolymer is characterized as having an isotactic triad (mm) measuredby ¹³C NMR of greater than about 0.85. Some such propylene-richalpha-olefin interpolymer comprise 5 to 25% by weight ofethylene-derived units and 95 to 75% by weight of propylene-derivedunits. Additionally, some propylene-rich alpha-olefin interpolymers have(a) a melting point of less than 90° C.; (b) a relationship ofelasticity to 500% tensile modulus such that the elasticity is less thanor equal to 0.935M+12, where elasticity is in percent and M is the 500%tensile modulus in MPa; and (c) a relationship of flexural modulus to500% tensile modulus such that flexural modulus is less than or equal to4.2e^(0.27M)+50, where flexural modulus is in MPa and M is the 500%tensile modulus in MPa. In some embodiments, the propylene richalpha-olefin interpolymer comprises 6 to 20% by weight ofethylene-derived units and 94 to 80% by weight of propylene-derivedunits. In other embodiments, polymers comprising 8 to 20% by weight ofethylene-derived units and 92 to 80% by weight of propylene-derivedunits are preferred. In still other embodiments, polymers comprising 10to 20% by weight of ethylene-derived units and 90 to 80% by weight ofpropylene-derived units.

In other embodiments, a propylene-rich alpha-olefin interpolymer thatcomprises a copolymer of propylene and at least one comonomer selectedfrom the group consisting of ethylene and C₄ to C₂₀ alpha-olefins,wherein the copolymer has a propylene content of greater than 65 molepercent, a weight average molecular weight (Mw) of from about 15,000 toabout 200,000, a weight average molecular weight/number averagemolecular weight ratio (Mw/Mn) of from about 1.5 to about 4.

Some thermoplastic resins or propylene-rich alpha-olefin interpolymersused in this aspect have a heat of fusion of less than about 80 J/g,preferably from about 8 to about 80, or more preferably from about 8 toabout 30 J/g as determined by DSC.

In some embodiments, the propylene-rich alpha-olefin interpolymer has acrystallinity of less than about 50%. In other embodiments, thecrystallinity ranges from about 5% to about 45%, or from about 5% toabout 40%.

In still other embodiments, the propylene-rich interpolymer has aflexural modulus, measured in accordance with ASTM D-790-97, of lessthan about 50 kpsi, preferably less than about 40 kpsi, more preferablyless than about 30 kpsi. In some dispersions, polymers having lowervalue for the flexural modulus are preferred. For example, some polymershave a flexural modulus of about 2 to about 15 kpsi, particularly about4 to about 10 kpsi.

Propylene-rich interpolymers or thermoplastic resins with a meltingpoint of less than about 140° C., preferably less than about 130° C.,more preferably less than about 120° C. are used. In some preferredembodiments, the propylene-rich interpolymer or thermoplastic resin hasa melting point of less than about 90° C.

Any suitable dispersing agent can be used in embodiments of this aspectof the invention. However, in particular embodiments, the dispersingagent comprises at least one carboxylic acid, a salt of at least onecarboxylic acid, carboxylic acid ester or salt of a carboxylic acidester. In some preferred embodiments, the carboxylic acid, the salt ofthe carboxylic acid, at least one carboxylic acid fragment of thecarboxylic acid ester or its salt has fewer than 25 carbon atoms. Inother embodiments, such moieties have 12 to 25 carbon atoms. In someembodiments, 15 to 25 carbon atoms are preferred. In other embodiments,the dispersing agent comprises at least one carboxylic acid, the salt ofthe at least one carboxylic acid, at least one carboxylic acid fragmentof the carboxylic acid ester or its salt that has 25 to 60 carbon atoms.Some preferred salts comprises a cation selected from the groupconsisting of an alkali metal cation, alkaline earth metal cation, orammonium or alkyl ammonium cation.

In still other embodiments, the dispersing agent is selected from thegroup consisting of ethylene acid polymers such as ethylene acrylic acidcopolymers or ethylene methacrylic acid copolymers.

In other embodiments, the dispersing agent is selected from alkyl ethercarboxylates, petroleum sulfonates, sulfonated polyoxyethylenatedalcohol, sulfated or phosphated polyoxyethylenated alcohols, polymericethylene oxide/propylene oxide/ethylene oxide dispersing agents, primaryand secondary alcohol ethoxylates, alkyl glycosides and alkylglycerides.

Combinations of any of the above-enumerated dispersing agents can alsobe used to prepared some aqueous dispersions.

Some dispersions described herein have an advantageous particle sizedistribution. In particular embodiments, the dispersion has a particlesize distribution defined as volume average particle diameter (Dv)divided by number average particle diameter (Dn) of less than or equalto about 2.0. In other embodiments, the dispersion has a particle sizedistribution of less than or equal to about 1.5.

Some dispersions described herein comprise particles having a volumeaverage particle size of less than about 1.5 μm. In other embodiments,the average particle size ranges from about 0.05 μm to about 1.5 μm. Instill other embodiments, the average particle size of the dispersionranges from about 0.5 μm to about 1.5 μm.

For dispersions having a pH of less than 12, some dispersions have a pHof from about 5 to about 11.5, preferably from about 7 to about 11, morepreferably from about 9 to about 11.

Preferably, the dispersions are characterized by a percent solidscontent of less than about 74% by volume. Some dispersions have apercent solids of from about 5% to about 74% by volume. Still otherdispersions have a percent solids of less than about 70% by volume, lessthan about 65% by volume, or from about 5% to about 50% by volume.

In another aspect, embodiments of the invention provide a method forproducing an aqueous dispersion comprising: (1) melt kneading (A) atleast one at least one propylene-rich alpha-olefin interpolymer, (B) atleast one dispersing agent, to form a melt-kneaded product; and (2)diluting said melt-kneaded product, and melt kneading the resultingmixture to form the aqueous dispersion. In particular embodiments, themethod includes diluting the melt kneaded product to provide adispersion having a pH of less than 12. Some methods provide adispersion with an average particle size of less than about 5 μm. Instill other embodiments, the method provides a dispersion that comprisesless than 4 percent by weight of the dispersing agent based on theweight of the polymer. Embodiments of the methods use the thermoplasticresins and dispersing agents described above. And in some embodiments,the methods provide dispersions having on or more of the propertiesdescribed above.

In still another aspect embodiments of the invention provide an aqueousdispersion comprising (A) at least one thermoplastic resin; (B) at leastone dispersing agent; and (C) water; wherein the thermoplastic resincomprises a propylene-rich alpha-olefin interpolymer comprising 5 to 25%by weight of ethylene-derived units and 95 to 75% by weight ofpropylene-derived units, the copolymer having: (a) a melting point ofless than 90° C.; (b) a relationship of elasticity to 500% tensilemodulus such that the elasticity is less than or equal to 0.935M+12,where elasticity is in percent and M is the 500% tensile modulus in MPa;and (c) a relationship of flexural modulus to 500% tensile modulus suchthat flexural modulus is less than or equal to 4.2e^(0.27M)+50, whereflexural modulus is in MPa and M is the 500% tensile modulus in MPa.

In another aspect of the invention, some dispersions are suitable formaking various articles. Some such articles include coatings, foams andfroths as well as decorative articles.

In one aspect, the present invention relates to a method for forming aheat sealable coating on a substrate, wherein the substrate is formedfrom at least one oriented polymer. In select embodiments, the methodincludes depositing an aqueous polymer dispersion on the substrate,wherein the aqueous polymer dispersion includes (A) at least onethermoplastic resin; (B) at least one dispersing agent; and (C) water;wherein the dispersion has a pH of less than 12, and drying thedispersion to form a first layer.

In one aspect, the present invention relates to a film layer thatincludes a substrate, the substrate including an oriented polymer,having a coating, wherein the coating was obtained from an aqueousdispersion comprising (A) at least one thermoplastic resin; (B) at leastone dispersing agent; and (C) water; wherein the dispersion had a pH ofless than 12.

In one aspect, the present invention relates to a film layer including asubstrate, the substrate including an oriented polymer, having acoating, wherein the coating was obtained from an aqueous dispersioncomprising (A) at least one thermoplastic resin; (B) at least onedispersing agent; and (C) water; wherein the dispersion had an averagevolume diameter particle size of less than about 5 μm.

In one aspect, the present invention relates to an article including asubstrate, the substrate including an oriented polymer, having acoating, wherein the coating was obtained from an aqueous dispersioncomprising (A) at least one thermoplastic resin; (B) at least onedispersing agent; and (C) water; wherein the dispersion had an averagevolume diameter particle size of less than about 5 μm.

In one aspect, the present invention relates to an article including asubstrate, the substrate including an oriented polymer, having acoating, wherein the coating was obtained from an aqueous dispersioncomprising (A) at least one thermoplastic resin; (B) at least onedispersing agent; and (C) water; wherein the dispersion had a pH of lessthan 12.

In one aspect, the present invention relates to a method for forming aheat sealable coating on a substrate including coating a substrate, withan aqueous polymer dispersion, wherein the aqueous polymer dispersioncomprises (A) at least one thermoplastic resin; (B) at least onedispersing agent; and (C) water; wherein the dispersion has a pH of lessthan 12; and orienting the substrate to form an oriented thermoplasticpolymer.

In one aspect, the present invention relates to a film layer including asubstrate, having a coating, wherein the film layer is characterized ashaving a heat seal initiation temperature of less than 80° C., andwherein the coating thickness is less than 2 microns.

Other aspects and advantages of the invention will be apparent from thefollowing description and the appended claims.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic representation of a typical melt-extrusionapparatus used to prepare embodiments of the invention.

FIG. 2 is a flowchart showing a method in accordance with an embodimentof the present invention.

FIG. 3 shows a graph of coat weights.

FIG. 4 shows a graph of heat seal data.

DETAILED DESCRIPTION

In the following description, all numbers disclosed herein areapproximate values, regardless whether the word “about” or “approximate”is used in connection therewith. They may vary by 1%, 2%, 5%, andsometimes, 10 to 20%. Whenever a numerical range with a lower limit,R_(L) and an upper limit, R_(U), is disclosed, any number falling withinthe range is specifically disclosed. In particular, the followingnumbers within the range are specifically disclosed:R=R_(L)+k*(R_(U)−R_(L)), wherein k is a variable ranging from 1% to 100%with a 1% increment, i.e., k is 1%, 2%, 3%, 4%, 5%, . . . , 50%, 51%,52%, . . . , 95%, 96%, 97%, 98%, 99%, or 100%. Moreover, any numericalrange defined by two R numbers as defined in the above is alsospecifically disclosed.

Embodiments of the invention relate to the dispersions outlined aboveand discussed in detail below. In addition, the present invention alsorelates to films and other products formed from such dispersions. Inparticular embodiments of the invention, dispersions made according tothe methods discussed herein are applied to a substrate (which may be apolymer film) to form a heat sealable layer. In specific embodiments,dispersions may be applied to a polypropylene substrate, which, in someembodiments may be biaxially oriented polypropylene.

Methods of the invention include applying an aqueous dispersion to anoriented substrate, either before or after the substrate has beenoriented. In other words, a method in accordance with one preferredembodiment of the present invention includes depositing an aqueousdispersion on an oriented substrate, and drying the dispersion to form aheat sealable layer.

In another embodiment, a method includes a depositing a coating on anunoriented substrate and then orienting the substrate. In this case, thecoating may be dried either before or after the orientation of thesubstrate.

In addition, the present inventors have discovered that by usingdispersions made with particular polyolefin polymers (which may besingle component polymer, or polymer blends), a heat sealable layer maybe formed that has a heat seal initiation temperature of 80° C. orbelow. In other embodiments, the heat seal initiation temperature may be75° C. or below. In other embodiments, the heat seal initiationtemperature may be 70° C. or below. In other embodiments, the heat sealinitiation temperature may be 65° C. or below.

The thermoplastic resin (A) included in embodiments of the aqueousdispersion of the present invention is a resin that is not readilydispersible in water by itself. In some embodiments it is present in thedispersion in an amount of from greater than 0 percent by wt. to lessthan about 96 percent by wt. In certain embodiments, the resin ispresent in an amount of from about 35 to about 65 percent by wt. of thedispersion. The term “resin” used herein should be construed to includesynthetic polymers or chemically modified natural resins such as but notlimited to thermoplastic materials such as polyvinyl chloride,polystyrene, and polyethylene and thermosetting materials such aspolyesters, epoxies, and silicones that are used with fillers,stabilizers, pigments, and other components to form plastics. The termresin as used herein includes elastomers and is understood to includeblends of olefin polymers. In some embodiments, the thermoplastic resinis a semicrystalline resin. The term “semi-crystalline” is intended toidentify those resins that possess at least one endotherm when subjectedto standard differential scanning calorimetry (DSC) evaluation. Somesemi-crystalline polymers exhibit a DSC endotherm that exhibits arelatively gentle slope as the scanning temperature is increased pastthe final endotherm maximum. This reflects a polymer of broad meltingrange rather than a polymer having what is generally considered to be asharp melting point. Some polymers useful in the dispersions of theinvention have a single melting point while other polymers have morethan one melting point. In some polymers one or more of the meltingpoints may be sharp such that all or a portion of the polymer melts overa fairly narrow temperature range, such as a few degrees centigrade. Inother embodiments, the polymer may exhibit broad melting characteristicsover a range of about 20° C. In yet other embodiments, the polymer mayexhibit broad melting characteristics over a range of greater than 50°C.

Examples of the thermoplastic resin (A) which may be used in the presentinvention include homopolymers and copolymers (including elastomers) ofan alpha-olefin such as ethylene, propylene, 1-butene,3-methyl-1-butene, 4-methyl-1-pentene, 3-methyl-1-pentene, 1-heptene,1-hexene, 1-octene, 1-decene, and 1-dodecene as typically represented bypolyethylene, polypropylene, poly-1-butene, poly-3-methyl-1-butene,poly-3-methyl-1-pentene, poly-4-methyl-1-pentene, ethylene-propylenecopolymer, ethylene-1-butene copolymer, and propylene-1-butenecopolymer; copolymers (including elastomers) of an alpha-olefin with aconjugated or non-conjugated diene as typically represented byethylene-butadiene copolymer and ethylene-ethylidene norbornenecopolymer; and polyolefins (including elastomers) such as copolymers oftwo or more alpha-olefins with a conjugated or non-conjugated diene astypically represented by ethylene-propylene-butadiene copolymer,ethylene-propylene-dicyclopentadiene copolymer,ethylene-propylene-1,5-hexadiene copolymer, andethylene-propylene-ethylidene norbornene copolymer; ethylene-vinylcompound copolymers such as ethylene-vinyl acetate copolymer,ethylene-vinyl alcohol copolymer, ethylene-vinyl chloride copolymer,ethylene acrylic acid or ethylene-(meth)acrylic acid copolymers, andethylene-(meth)acrylate copolymer; styrenic copolymers (includingelastomers) such as polystyrene, ABS, acrylonitrile-styrene copolymer,α-methylstyrene-styrene copolymer; and styrene block copolymers(including elastomers) such as styrene-butadiene copolymer and hydratethereof, and styrene-isoprene-styrene triblock copolymer; polyvinylcompounds such as polyvinyl chloride, polyvinylidene chloride, vinylchloride-vinylidene chloride copolymer, polymethyl acrylate, andpolymethyl methacrylate; polyamides such as nylon 6, nylon 6,6, andnylon 12; thermoplastic polyesters such as polyethylene terephthalateand polybutylene terephthalate; polycarbonate, polyphenylene oxide, andthe like. These resins may be used either alone or in combinations oftwo or more.

In particular embodiments, polyolefins such as polypropylene,polyethylene, and copolymers thereof and blends thereof, as well asethylene-propylene-diene terpolymers. In some embodiments, preferredolefinic polymers include homogeneous polymers described in U.S. Pat.No. 3,645,992 by Elston; high density polyethylene (HDPE) as describedin U.S. Pat. No. 4,076,698 to Anderson; heterogeneously branched linearlow density polyethylene (LLDPE); heterogeneously branched ultra lowlinear density (ULDPE); homogeneously branched, linearethylene/alpha-olefin copolymers; homogeneously branched, substantiallylinear ethylene/alpha-olefin polymers which can be prepared, forexample, by a process disclosed in U.S. Pat. Nos. 5,272,236 and5,278,272, the disclosure of which process is incorporated herein byreference; and high pressure, free radical polymerized ethylene polymersand copolymers such as low density polyethylene (LDPE), ethylene-acrylicacid (EAA) and Ethylene-methacrylic acid copolymers such as for examplethose available under the tradenames PRIMACOR™, Nucrel™, and Escor™ anddescribed in U.S. Pat. Nos. 4,599,392, 4,988,781, and 59,384,373, eachof which is incorporated herein by reference in its entirety, andethylene-vinyl acetate (EVA) copolymers. Polymer compositions describedin U.S. Pat. Nos. 6,538,070, 6,566,446, 5,869,575, 6,448,341, 5,677,383,6,316,549, 6,111,023, or 5,844,045, each of which is incorporated hereinby reference in its entirety, are also suitable in some embodiments. Ofcourse, blends of polymers can be used as well. In some embodiments theblends include two different Ziegler-Natta polymers. In otherembodiments, the blends can include blends of a Ziegler-Natta and ametallocene polymer. In still other embodiments, the thermoplastic resinused herein is a blend of two different metallocene polymers.

In some particular embodiments, the thermoplastic resin is apropylene-based copolymer or interpolymer. In some embodiments thepropylene/ethylene copolymer or interpolymer is characterized as havingsubstantially isotactic propylene sequences. The term “substantiallyisotactic propylene sequences” and similar terms mean that the sequenceshave an isotactic triad (mm) measured by 13C NMR of greater than about0.85, preferably greater than about 0.90, more preferably greater thanabout 0.92 and most preferably greater than about 0.93. Isotactic triadsare well-known in the art and are described in, for example, U.S. Pat.No. 5,504,172 and WO 00/01745, which refer to the isotactic sequence interms of a triad unit in the copolymer molecular chain determined by ¹³CNMR spectra. NMR spectra are determined as described below. Preferably,when the aqueous dispersions comprise a propylene/ethylene interpolymer,the ethylene is present in an amount of from about 5% to about 25% (byweight).

¹³C NMR spectroscopy is one of a number of techniques known in the artof measuring comonomer incorporation into a polymer and measuringisotactic triad levels in propylene-based copolymers. An example of thistechnique is described for the determination of comonomer content forethylene/α-olefin copolymers in Randall (Journal of MacromolecularScience, Reviews in Macromolecular Chemistry and Physics, C29 (2 & 3),201-317 (1989)). The basic procedure for determining the comonomercontent of an olefin interpolymer involves obtaining the ¹³C NMRspectrum under conditions where the intensity of the peaks correspondingto the different carbons in the sample is directly proportional to thetotal number of contributing nuclei in the sample. Methods for ensuringthis proportionality are known in the art and involve allowance forsufficient time for relaxation after a pulse, the use ofgated-decoupling techniques, relaxation agents, and the like. Therelative intensity of a peak or group of peaks is obtained in practicefrom its computer-generated integral. After obtaining the spectrum andintegrating the peaks, those peaks associated with the comonomer areassigned. This assignment can be made by reference to known spectra orliterature, or by synthesis and analysis of model compounds, or by theuse of isotopically labeled comonomer. The mole % comonomer can bedetermined by the ratio of the integrals corresponding to the number ofmoles of comonomer to the integrals corresponding to the number of molesof all of the monomers in the interpolymer, as described in Randall, forexample.

The data is collected using a Varian UNITY Plus 400 MHz NMRspectrometer, corresponding to a ¹³C resonance frequency of 100.4 MHz.Acquisition parameters are selected to ensure quantitative ¹³C dataacquisition in the presence of the relaxation agent. The data isacquired using gated 1H decoupling, 4000 transients per data file, a 7sec pulse repetition delay, spectral width of 24,200 Hz and a file sizeof 32K data points, with the probe head heated to 130° C. The sample isprepared by adding approximately 3 mL of a 50/50 mixture oftetrachloroethane-d2/orthodichlorobenzene that is 0.025M in chromiumacetylacetonate (relaxation agent) to 0.4 g sample in a 10 mm NMR tube.The headspace of the tube is purged of oxygen by displacement with purenitrogen. The sample is dissolved and homogenized by heating the tubeand its contents to 150° C. with periodic refluxing initiated by heatgun.

Preferably, the propylene/ethylene interpolymer has a crystallinity ofless than about 50% and a flexural modulus, measured in accordance withASTM D-790-97, of less than about 50 kpsi, preferably less than about 40kpsi, and especially less than about 30 kpsi. Preferably, thepropylene/ethylene interpolymer has a melting point of less than about140° C., preferably less than about 130° C., more preferably less thanabout 120° C., especially less than about 90° C. The propylene/ethyleneinterpolymers used in the dispersions also preferably have a heat offusion of less than 80 J/gm, more preferably less than about 75 J/gm,more preferably less than about 50 J/gm, and can be as low as about 8J/gm, or as low as 4 J/gm.

In some preferred dispersions, the propylene-based copolymer comprises apropylene-ethylene copolymer made using a nonmetallocene,metal-centered, heteroaryl ligand catalyst as described in U.S.Published Patent Application No. 20030204017 filed May 5, 2002, which isincorporated by reference herein in its entirety for its teachingsregarding such catalysts. The propylene-ethylene copolymers made withsuch nonmetallocene, metal-centered, heteroaryl ligand catalyst exhibita unique regio-error. The regio-error is identified by ¹³C NMR peakscorresponding at about 14.6 and about 15.7 ppm, which are believed to bethe result of stereo-selective 2,1-insertion errors of propylene unitsinto the growing polymer chain. In this particularly preferred aspect,these peaks are of about equal intensity, and they typically representabout 0.02 to about 7 mole percent of the propylene insertions into thehomopolymer or copolymer chain.

In some aspects of the invention, the propylene-based copolymer has amolecular weight distribution (MWD), defined as weight average molecularweight divided by number average molecular weight (Mw/Mn) of about 4 orless, and can be as low as about 1.5.

Molecular weight distribution of the polymers is determined using gelpermeation chromatography (GPC) on a Polymer Laboratories PL-GPC-220high temperature chromatographic unit equipped with four linear mixedbed columns (Polymer Laboratories (20-micron particle size)). The oventemperature is at 160° C. with the autosampler hot zone at 160° C. andthe warm zone at 145° C. The solvent is 1,2,4-trichlorobenzenecontaining 200 ppm 2,6-di-t-butyl-4-methylphenol. The flow rate is 1.0milliliter/minute and the injection size is 100 microliters. About 0.2%by weight solutions of the samples are prepared for injection bydissolving the sample in nitrogen purged 1,2,4-trichlorobenzenecontaining 200 ppm 2,6-di-t-butyl-4-methylphenol for 2.5 hrs at 160° C.with gentle mixing.

The molecular weight determination is deduced by using ten narrowmolecular weight distribution polystyrene standards (from PolymerLaboratories, EasiCal PS1 ranging from 580-7,500,000 g/mole) inconjunction with their elution volumes. The equivalentpropylene-ethylene copolymer molecular weights are determined by usingappropriate Mark-Houwink coefficients for polypropylene (as described byTh. G. Scholte, N. L. J. Meijerink, H. M. Schoffeleers, and A. M. G.Brands, J. Appl. Polym. Sci., 29, 3763-3782 (1984)) and polystyrene (asdescribed by E. P. Otocka, R. J. Roe, N. Y. Hellman, P. M. Muglia,Macromolecules, 4, 507 (1971)) in the Mark-Houwink equation:

{N}=KMa

where Kpp=1.90E-04, app=0.725 and Kps=1.26E-04, aps=0.702.

In one embodiment of the invention, the thermoplastic resins utilized inthe invention are characterized by a DSC curve with a Tme that remainsessentially the same and a Tmax that decreases as the amount ofunsaturated comonomer in the copolymer is increased. Tme means thetemperature at which the melting ends and Tmax means the peak meltingtemperature, both as determined by one of ordinary skill in the art fromDSC analysis using data from the final heating step. For such polymers,DSC analysis can be determined using a model Q1000 DSC from TAInstruments, Inc., which is calibrated using indium and deionized water.

In some other embodiments, thermoplastic polymer compositions disclosedin U.S. Pat. No. 6,525,157, incorporated by reference in its entirety.The polymers described therein comprise a majority of propylene with aminor amount of ethylene. These polymer compositions include a linear,single homogeneous macromolecular copolymer structure. These polymershave limited crystallinity due to adjacent isotactic propylene units andhave a melting point as described below. They are generally devoid ofany substantial intermolecular heterogeneity in tacticity and comonomercomposition, and are substantially free of diene. They are also devoidof any substantial heterogeneity in intramolecular compositiondistribution.

In some embodiments of the dispersions described herein, the copolymerincludes from a lower limit of 5% or 6% or 8% or 10% by weightethylene-derived units to an upper limit of 20% or 25% by weightethylene-derived units. These embodiments also will includepropylene-derived units present in the copolymer in the range of from alower limit of 75% or 80% by weight to an upper limit of 95% or 94% or92% or 90% by weight. These percentages by weight are based on the totalweight of the propylene and ethylene-derived units; i.e., based on thesum of weight percent propylene-derived units and weight percentethylene-derived units being 100%. Within these ranges, these copolymersare mildly crystalline as measured by differential scanning calorimetry(DSC), and exhibit elasticity. Elasticity, as defined in detailhereinbelow, is a dimensional recovery from elongation for thesecopolymers.

In embodiments of our invention, a thermoplastic resin is includedhaving a weight average molecular weight (Mw) of from 15,000-5,000,000,or from 20,000 to 1,000,000 and a molecular weight distribution Mw/Mn(sometimes referred to as a “polydispersity index” (PDI)) ranging from alower limit of 1.01, 1.5 or 1.8 to an upper limit of 40 or 20 or 10 or 5or 3. In other embodiments the Mw may range from 10,000 to 300,000, orfrom 100,000 to 250,000.

Another measure of molecular weight typically used for polyethylenepolymers is the melt index of the polymer, also called I₂. The meltindex is indirectly proportional to the molecular weight, although therelationship is not linear. For polyethylene the melt index is measuredaccording to ASTM D-1238, condition 190 deg C./2.16 kg). Typicalthermoplastic resins useful in embodiments of the invention have an I₂in the range of from 0.001 to 1000 g/10 min. In some embodiments, thethermoplastic resin (A) has an I₂ of from 0.5 to 500 g/10 min. Otherembodiments include a thermoplastic resin with an I₂ of from 1 to 300g/10 min. The selection of suitable I₂ for the thermoplastic resinshould be selected in view of the ease of melt kneadability and physicalproperties of the coating formed.

Melt flow rate (MFR) is another way of measuring the molecular weight ofpolypropylene polymers. Like melt index, MFR is indirectly proportionalto the molecular weight, although the relationship is not linear. MFR istypically measured according to ASTM D-1238, condition 230° deg C./2.16kg). Typical thermoplastic resins useful in embodiments of the inventionhave an MFR less than about 250 g/10 min. In some embodiments, thethermoplastic resin (A) has an MFR of from about 1 to about 200 g/10min. Other embodiments include a thermoplastic resin with an MFR of from5 to 100 g/10 min

Melting Point and Crystallinity

Differential scanning calorimetry (DSC) is a common technique that canbe used to examine the melting and crystallization of semi-crystallinepolymers. General principles of DSC measurements and applications of DSCto studying semi-crystalline polymers are described in standard texts(e.g., E. A. Turi, ed., Thermal Characterization of Polymeric Materials,Academic Press, 1981). For example, DSC analysis may be determined usinga model Q1000 DSC from TA Instruments, Inc, which is calibrated usingindium and deionized water. After heating the sample rapidly to 230 Cand holding for 3 minutes, the cooling curve is obtained by cooling at10 C/min to −40 C. After holding at −40 C for 3 minutes, the DSC meltingendotherm is recorded while heating at 10 C/min. The melting point isdetermined using the standard TA DSC software.

These propylene-rich polymers can be made by a number of processes, suchas by single stage, steady state, polymerization conducted in awell-mixed continuous feed polymerization reactor. In addition tosolution polymerization, other polymerization procedures such as gasphase or slurry polymerization may be used. Other details suitableprocesses for preparing such polymers are described in U.S. Pat. No.6,525,157, incorporated by reference in its entirety.

A typical isotactic polymerization process consists of a polymerizationin the presence of a catalyst including a bis(cyclopentadienyl) metalcompound and either (1) a non-coordinating compatible anion activator,or (2) an alumoxane activator. According to one embodiment of theinvention, this process comprises the steps of contacting ethylene andpropylene with a catalyst in a suitable polymerization diluent, thecatalyst including, in one embodiment, a chiral metallocene compound,e.g., a bis(cyclopentadienyl) metal compound as described in U.S. Pat.No. 5,198,401, and an activator. U.S. Pat. No. 5,391,629 also describescatalysts useful to produce the some copolymers suitable in dispersionsdescribed herein. Gas phase polymerization processes are described inU.S. Pat. Nos. 4,543,399, 4,588,790, 5,028,670, for example. Methods ofsupporting metallocene catalysts useful for making some copolymers usedembodiments of the invention are described in U.S. Pat. Nos. 4,808,561,4,897,455, 4,937,301, 4,937,217, 4,912,075, 5,008,228, 5,086,025,5,147,949, and 5,238,892. Numerous examples of the biscyclopentadienylmetallocenes described above for the invention are disclosed in U.S.Pat. Nos. 5,324,800; 5,198,401; 5,278,119; 5,387,568; 5,120,867;5,017,714; 4,871,705; 4,542,199; 4,752,597; 5,132,262; 5,391,629;5,243,001; 5,278,264; 5,296,434; and 5,304,614. Descriptions of ioniccatalysts for coordination polymerization including metallocene cationsactivated by non-coordinating anions appear in the early work in EP-A-0277 003, EP-A-0 277 004, U.S. Pat. Nos. 5,198,401 and 5,278,119, and WO92/00333. The use of ionizing ionic compounds not containing an activeproton but capable of producing both the active metallocene cation and anon-coordinating anion is also known. See, EP-A-0 426 637, EP-A-0 573403 and U.S. Pat. No. 5,387,568, EP-A-0 427 697 and EP-A-0 520 732.Ionic catalysts for addition polymerization can also be prepared byoxidation of the metal centers of transition metal compounds by anionicprecursors containing metallic oxidizing groups along with the aniongroups; see EP-A-0 495 375.

Some polymers can be prepared by a polymerization process comprising:reacting propylene and at least one comonomer selected from the groupconsisting of ethylene and at least one C₄ to C₂₀ alpha-olefin, underpolymerization conditions in the presence of a metallocene catalystcapable of incorporating the propylene sequences into isotactic orsyndiotactic orientations, in at least one reactor to produce a firstcopolymer having at least 65 mole % propylene and wherein preferably atleast 40% of the propylene sequences are in isotactic or syndiotacticorientations; wherein the copolymer has a melt index (MI) from about 7dg/min to about 3000 dg/min. Some details of the polymers are describedin the following paragraphs.

Preferably, a substantial portion of the propylene-rich polymer orpolymer blend melts within 40 to 120° C. One of ordinary skill in theart will appreciate that initiation of melt may begin at lowertemperatures. Also, the polymer or polymer blend preferably includesethylene (or an alpha olefin, e.g., having from 4-20 carbon atoms) inthe amount of up to 30 mole %, preferably from 3 mole % to 20 mole % andmore preferably from 7 mole % to 15 mole wt %. In this context, theethylene or alpha olefin can be units forming part of a randomsemicrystalline copolymer that includes both propylene units andethylene units, e.g., when a single copolymer is used (not a blend).Alternatively, a blend can be used in which isotactic polypropylene isblended with a polyethylene, in which case the ethylene units in thepolyethylene should be up to 30 mole % of the overall polymer blend.

In other specific embodiments, the dispersions include a propylene-richpolymer or polymer blends wherein the composition preferably includes arandom copolymer produced by copolymerizing propylene and at least oneof ethylene or alpha-olefin having 20 or less carbon atoms, preferably 8or less carbon atoms, the random copolymer having a crystallinity atleast about 2% and no greater than about 65% derived from stereoregularpolypropylene sequences and a melting point of from about 25° C. toabout 105° C.

In still other specific embodiments, the propylene-rich copolymers arethe reaction product of a free radical initiator and a random copolymerproduced by copolymerizing propylene and at least one of ethylene oralpha-olefin having 8 or less carbon atoms, the random copolymer havinga crystallinity at least about 2% and no greater than about 65% derivedfrom stereoregular polypropylene sequences and a melting point of fromabout 25° C. to about 105° C.

In yet another specific embodiment of this invention the dispersionincludes a random polymer with a melting point between about 40° C. and140° C. The viscosity as measured by melt flow rate at 230° C. should bebetween 2 and 5600, more preferably between 70 and 370, and mostpreferably between 300 and 1800. Correspondingly, the melt index,measured at 190° C., should be between 20 and 1500, more preferablybetween 40 and 1000, and most preferably between 100 and 500. Further,the tensile elongation of the polymer at room temperature should be inexcess of 50%, more preferably in excess of 100%, and most preferably inexcess of 300%. Preferably, the random copolymer is a low molecularweight copolymer containing propylene units in an amount of 80% orabove, preferably more than 90%, with the propylene units preferablybeing predominantly isotactic sequences (more than 80% of the unitsbeing isotactic pentads), as measured by ¹³C NMR. The random copolymerscan have long chain branching, providing greater flexibility for desiredrheological properties.

Still other dispersions can include a polyolefin composition containinga physical blend, wherein an ethylene-propylene copolymer is blendedtogether with isotactic polypropylene. Those ethylene-propylenecopolymers are preferably derived by solution polymerization usingchiral metallocene catalysts. Those ethylene-propylene copolymerspreferably have crystallinity derived from isotactic propylenesequences. In those blend compositions, the composition of thecopolymers includes up to 30 wt % and preferably up to 20 wt % ethylene.Those copolymers may be linear or branched. Those blends preferablycontain substantial amounts of isotactic polypropylene, at least about 5to 10 wt %. In a specific embodiment, the blend can include isotacticpolypropylene in an amount up to about 50 wt %, or alternatively up toabout 80 wt %. The blend can also include other olefin-based polymers,such as reactor copolymers and impact copolymers. Desirably, the use ofthe blends described above provide for favorable melting temperaturesdue to the presence of the isotactic polypropylene while providing aseparate molecular architecture for the copolymer, thus improving therheology, elasticity and flexibility of the adhesive composition.

In still other embodiments, some dispersions include a thermoplasticresin selected from copolymers and interpolymers of ethylene and/orpropylene and other monomers selected from C₄ to C₁₀ olefins, preferablyalpha-olefins, more preferably from C₄ to C₈ alpha-olefins and mostpreferably selected from n-butene, n-hexene and n-octene. The ethyleneor propylene content of the thermoplastic resin ranges from about 2-98wt. percent of the resin.

In some embodiments, a primarily ethylene-based polyolefin is selectedin which ethylene comprises from about 98 to 65 percent of polymer. Inother embodiments, a primarily propylene-based polyolefin may beselected, propylene comprising from about 98 to 65 percent of thePolymer. Selected comonomer(s) make up the remainder of the polymer.

In some such embodiments, the ethylene polymer has the followingcharacteristics and properties: 1) Crystallinity as determined by theobservance of at least one endotherm when subjected to standarddifferential scanning calorimetry (DSC) evaluation; 2) a melt index ofbetween about 30 and about 0.1 g/10 min, preferably of between 25 and0.25 g/10 min, more preferably of between 22 and 0.5 g/10 min and mostpreferably of between 18 and 0.75 g/10 min; and 3) a density asdetermined according to ASTM D-792 of between about 0.845 and about0.925 g/cc, preferably between 0.85 10 and 0.91 g/cc, and morepreferably between 0.855 and 0.905 g/cc, and most preferably between0.86 and 0.90 g/cc.

One class of resins particularly suited to use in embodiments of theinvention are copolymers of ethylene and 1-octene or 1-butene, whereethylene comprises from about 90 to about 50, more preferably 85 to 55,and 1-octene or 1-butene from about 10 to about 50, more preferablyabout 15 to 45 percent by weight of the copolymer, and that have MeltIndex of between about 0.25 and about 30, more preferably between 0.5and 20 g/10 min. Alternatively, instead of a single Polymer a blend ofpolymers may be employed that has the physical characteristics describedabove. For example, it may be desirable to blend a first polymer withrelatively high MI that is outside the range described above, withanother of relatively low MI, so that the combined MI and the averageddensity of the blend fall within the ranges noted above.

In addition to the thermoplastic resin, dispersions described hereininclude a dispersing agent. Any dispersing agent may be used inembodiments of the invention. As used herein the term “dispersing agent”means an agent that aids in the formation and/or the stabilization of andispersion. Some dispersing agents can also be used to form emulsionsand are described in detail by Paul Becher (Emulsions: Theory andPractice, 3rd edition, Oxford University Press, New York, 2001),incorporated herein by reference in its entirety. Dispersing agentsgenerally fall into three classes 1) surface-active materials, 2)naturally occurring materials, 3) finely divided solids. Surface-activeagents, also called surfactants, are materials that reduce theinterfacial tension between two immiscible liquid phases. They areclassified according to the hydrophilic group in the molecule: anionic,cationic, nonionic, or ampholytic (amphoteric). Examples of commerciallyavailable dispersing agents is found in McCutcheon (McCutcheon'sEmulsifiers and Detergents, Glen Rock, N.J., issued annually). Examplesof naturally occurring materials include phospholipids, sterols,lanolin, water-soluble gums, alginates, carrageenin, and cellulosederivatives. Examples of finely divided solids include basic salts ofthe metals, carbon black, powdered silica, and various clay (principallybentonite).

In some embodiments, a carboxylic acid or carboxylic acid salt is usedas the dispersing agent. Typical salts include an alkali metal salt oran alkaline earth metal salts of the fatty acid. Other salts includeammonium or alkyl ammonium salts of the carboxylic acid. In someembodiments, the carboxylic acid or it's salt with 12 to fewer than 25carbon atoms. Where the dispersing agent is a salt, the number ofcarbons refers to the carbon atoms associated with the carboxylic acidfragment. In other embodiments, the salt is formed with a fatty acidfragment that has at from 15 to 25 carbon atoms. Particular embodimentsuse an alkali metal salt of erucic acid. Erucic acid is a carboxylicacid with 22 carbon atoms. Some embodiments use erucic acid in the formof rapeseed oil which is a natural oil that contains approximately 40 toabout 50% erucic acid with the remainder consisting of primarily chainshaving 18 carbon atoms. An alkali metal salt of erucic acid is alsouseful in some embodiments.

Some embodiments of the present invention use a fatty acid or its saltthat is derived from an ester of a fatty acid. The alcohol residueconstituting such ester may preferably contain 2 to 30 carbon atoms, andmost preferably 6 to 20 carbon atoms. Such residue may be either astraight or a branched residue, and may also be a mixture of two or moreresidues each containing different number of carbon atoms. Exemplarysuch alcohol residues include residues of higher alcohols containing 10to 20 carbon atoms such as cetyl alcohol, stearyl alcohol, and oleylalcohol. Some embodiments use an ester wax of erucic acid.

In particular embodiments the salt of a fatty acid containing fewer than25 carbon atoms is produced by neutralizing a fatty acid containingfewer than 25 carbon atoms or by saponification of an ester of a fattyacid containing fewer than 25 carbon atoms.

In other embodiments, the dispersing agent can be an ethylene acrylicacid copolymer. Still other embodiments use alkyl ether carboxylates asthe dispersing agent. In some embodiments, petroleum sulfonates areuseful. In other embodiments, the dispersing agent is a sulfonated orpolyoxyethylenated alcohol. In still other embodiments, sulfated orphosphated polyoxyethylenated alcohols are suitable. Polymeric ethyleneoxide/propylene oxide/ethylene oxide dispersing agents, known aspoloxamers are used as the dispersing agent. Primary and secondaryalcohol ethoxylates are also suitable in some dispersions. Alkylglycosides and alkyl glycerides are used in some dispersions. Of course,combinations of these dispersing agents are also suitable.

Embodiments of the aqueous dispersions described herein contain water inaddition to the components as described above. Deionized water istypically preferred. In some embodiments, water with excess hardness canundesirably affect the formation of a suitable dispersion. Particularlywater containing high levels of alkaline earth ions, such as Ca²⁺,should be avoided. The term “dispersion” as used herein refers to afinely divided solid or liquid in a continuous liquid medium. An aqueousdispersion is a dispersion in which the continuous liquid medium iswater. The term “dispersion” as used herein in connection with thecompositions of the invention is intended to include within its scopeboth emulsions of essentially liquid materials, prepared employing thethermoplastic resin and the dispersing agent, and dispersions of solidparticles. Such solid dispersions can be obtained, for example, bypreparing an emulsion as previously described, and then causing theemulsion particle to solidify by various means. Thus, when thecomponents are combined, some embodiments provide an aqueous dispersionwherein content of the dispersing agent is present in the range of from0.5 to 30 parts by weight, and content of (C) water is in the range of 1to 35% by weight per 100 parts by weight of the thermoplastic polymer;and total content of (A) and (B) is in the range of from 65 to 99% byweight. In particular embodiments, the dispersing agent ranges from 2 to20 parts by weight based on 100 parts by weight of the polymer. In someembodiments, the amount of dispersing agent is less than about 4 percentby wt., based on the weight of the thermoplastic polymer. In someembodiments, the dispersing agent comprises from about 0.5 percent bywt. to about 3 percent by weight, based on the amount of thethermoplastic polymer used. In other embodiments, about 1.0 to about 3.0weight percent of the dispersing agent are used. Embodiments having lessthan about 4 weight percent dispersing agent are preferred where thedispersing agent is a carboxylic acid.

One feature of some embodiments of the invention is that the dispersionshave a small particle size. Typically the average particle size is lessthan about 5 μm. Some preferred dispersions have an average particlesize of less than about 1.5 μm. In some embodiments, the upper limit onthe average particle size is about 4.5 μm, 4.0 μm, 3.5 μm, 3.75 μm, 3.5μm, 3.0 μm, 2.5 μm, 2.0 μm, 1.5 μm, 1.0 μm, 0.5 μm, or 0.1 μm. Someembodiments have a lower limit on the average particle size of about0.05, 0.7 μm, 0.1 μm, 0.5 μm, 1.0 μm, 1.5 μm, 2.0 μm, or 2.5 μm. Thus,some particular embodiments have, for example, an average particle sizeof from about 0.05 μm to about 1.5 μm. While in other embodiments, theparticles in the dispersion have an average particle size of from about0.5 μm to about 1.5 μm. For particles that are not spherical thediameter of the particle is the average of the long and short axes ofthe particle. Particle sizes can be measured on a Coulter LS230light-scattering particle size analyzer or other suitable device.

Another parameter that characterizes particles in the dispersions is theparticle size distribution, defined herein as the volume averageparticle diameter (Dv) divided by number average particle diameter (Dn).Some embodiments are characterized by a particle size distribution ofless than or equal to about 2.0. In other embodiments, the dispersionshave a particle size distribution of less than or equal to about lessthan 1.9, 1.7, or 1.5.

In yet another particular embodiment the aqueous dispersion has aconcentration of the solid content including (A) thermoplastic resin isin the range of from 10 to 70%. Another measure of solids content is byvolume. In some embodiments, the dispersion has a percent solids of lessthan about 74% by volume. Other dispersions have a solids content offrom about 5% to about 74% by volume. In some embodiments, thedispersions have a percent solids of less than about 70% by volume, lessthan about 65% by volume, or ranging from about 5% to about 50% byvolume.

One feature of some of the dispersions described herein is the pH, whichcan affect the uses for which dispersions are suitable. Typically, thedispersions have a pH of less than 12. Preferably, the pH ranges fromabout 5 to about 11.5, preferably from about 7 to about 11, morepreferably from about 9 to about 11. However, dispersions having a lowerlimit of the pH of about 5, about 6, about 7, about 8, about 9, about10, or about 11 are contemplated. Dispersions having an upper limit onthe pH of about 6, about 7, about 8, about 9, about 10, about 11, orabout 12 are contemplated.

While any method may be used, one convenient way to prepare thedispersions described herein is by melt-kneading. Any melt kneadingmeans known in the art may be used. In some embodiments a kneader, aBanbury mixer, single-screw extruder, or a multi-screw extruder is used.The melt kneading may be conducted under the conditions which aretypically used for melt kneading the thermoplastic resin (A). A processfor producing the dispersions in accordance with the present inventionis not particularly limited. One preferred process, for example, is aprocess comprises melt-kneading the above-mentioned components accordingto U.S. Pat. No. 5,756,659 and U.S. Patent Application No. 20010011118.A preferred melt-kneading machine is, for example, a multi screwextruder having two or more screws, to which a kneading block can beadded at any position of the screws. If desired, it is allowable thatthe extruder is provided with a first material-supplying inlet and asecond material-supplying inlet, and further third and forthmaterial-supplying inlets in this order from the upper stream to thedown stream along the flow direction of a material to be kneaded.Further, if desired, a vacuum vent may be added at an optional positionof the extruder. In some embodiments, the dispersion is first diluted tocontain about 1 to about 3% by weight of water and then subsequentlyfurther diluted to comprise greater than 25% by weight of water. In someembodiments, the further dilution provides a dispersion with at leastabout 30% by weight of water. The aqueous dispersion obtained by themelt kneading may be further supplemented with an aqueous dispersion ofan ethylene-vinyl compound copolymer, or a dispersing agent.

FIG. 1 schematically illustrates such an extrusion apparatus embodimentsof the invention. An extruder, in certain embodiments a twin screwextruder, 20 is coupled to a back pressure regulator, melt pump, or gearpump, 30. Embodiments also provide a base reservoir 40 and an initialwater reservoir 50, each of which includes a pump (not shown). Desiredamounts of base and initial water are provided from the base reservoir40 and the initial water reservoir 50, respectively. Any suitable pumpmay be used, but in some embodiments a pump that provides a flow ofabout 150 cc/min at a pressure of 240 bar is used to provide the baseand the initial water to the extruder 20. In other embodiments, a liquidinjection pump provides a flow of 300 cc/min at 200 bar or 600 cc/min at133 bar. In some embodiments the base and initial water are preheated ina preheater.

Resin in the form of pellets, powder or flakes is fed from the feeder 80to an inlet 90 of the extruder 20 where the resin is melted orcompounded. In some embodiments, the dispersing agent is added to theresin through an opening along with the resin and in other embodiments,the dispersing agent is provided separately to the twin screw extruder20. The resin melt is then delivered from the mix and convey zone to anemulsification zone of the extruder where the initial amount of waterand base from the reservoirs 40 and 50 is added through inlet 55. Insome embodiments, dispersing agent may be added additionally orexclusively to the water stream. In some embodiments, the emulsifiedmixture is further diluted with additional water via inlet 95 fromreservoir 60 in a dilution and cooling zone of the extruder 20.Typically, the dispersion is diluted to at least 30 weight percent waterin the cooling zone. In addition, the diluted mixture may be diluted anynumber of times until the desired dilution level is achieved. In someembodiments, water is not added into the twin screw extruder 20 butrather to a stream containing the resin melt after the melt has exitedfrom the extruder. In this manner, steam pressure build-up in theextruder 20 is eliminated.

In some embodiments a basic substance or aqueous solution, dispersion orslurry thereof is added to the dispersion at any point of the process,preferably to the extruder. Typically the basic substance is added as anaqueous solution. But in some embodiments, it is added in otherconvenient forms, such as pellets or granules. In some embodiments, thebasic substance and water are added through separate inlets of theextruder. Examples of the basic substance which may be used for theneutralization or the saponification in the melt kneading processinclude alkaline metals and alkaline earth metals such as sodium,potassium, calcium, strontium, barium; inorganic amines such ashydroxylamine or hydrazine; organic amines such as methylamine,ethylamine, ethanolamine, cyclohexylamine, tetramethylammoniumhydroxide; oxide, hydroxide, and hydride of alkaline metals and alkalineearth metals such as sodium oxide, sodium peroxide, potassium oxide,potassium peroxide, calcium oxide, strontium oxide, barium oxide, sodiumhydroxide, potassium hydroxide, calcium hydroxide, strontium hydride,barium hydroxide, sodium hydride, potassium hydride, calcium hydride;and weak acid salts of alkaline metals and alkaline earth metals such assodium carbonate, potassium carbonate, sodium hydrogencarbonate,potassium hydrogencarbonate, calcium hydrogencarbonate, sodium acetate,potassium acetate, calcium acetate; or ammonium hydroxide. In particularembodiments, the basic substance is a hydroxide of an alkaline metal ora hydroxide of an alkali metal. In some embodiments, the basic substanceis selected from potassium hydroxide, sodium hydroxide and combinationsthereof.

The aqueous dispersion may be coated onto a substrate by variousprocedures, and for example, by spray coating, curtain flow coating,coating with a roll coater or a gravure coater, brush coating, dipping.The coating is preferably dried by heating the coated substrate to 50 to150° C. for 1 to 300 seconds although the drying may be accomplished byany suitable means.

The substrate for coatings may comprise a film of a thermoplastic resinsuch as polypropylene, polyethylene terephthalate, polyethylene, otherpolyolefins, oriented polyolefins, such as biaxially orientedpolypropylene, polycarbonate, polyimide, polyamide, polyphenylenesulfide, polysulfone, aromatic polyester, polyether ether ketone,polyether sulfone, and polyether imide. The preferred substrate is afilm comprising polyethylene terephthalate, polyethylene, polyamide,and/or polycarbonate, and the most preferred substrate is a filmcomprising polypropylene, and in particular, biaxially orientedpolypropylene. Typically the films have a thickness in the range of from0.5 to 50 microns, although some have a thickness of from 1 to 30microns.

Some embodiments of the dispersions described herein are capable offorming a coating which exhibits excellent water resistance, oilresistance, or chemical resistance. Some embodiments exhibit adhesion tonon-polar materials, and therefore, when the aqueous dispersion of thepresent invention is coated and dried on the surface of a substrate suchas paper, fiber, wood, metal, or plastic molded article, the resultingresin coating will provide the substrate with water resistance, oilresistance, chemical resistance, corrosion resistance and heatsealability. Coatings obtained from some dispersions described hereinexhibit excellent moisture resistance, water repellency, thermaladhesion to paper, especially for water and/or grease barrier and inkadhesion coatings layers, metal, glass, wood, fiber (natural fiber andsynthetic fiber), and nonwoven fabric, thermal transfer properties,abrasion resistance, impact resistance, weatherability, solventresistance, flexibility, and adaptability to high-frequency fabricating.Some dispersions are particularly suited for the formation of textilecoatings including fabric impregnation. Some dispersions are alsosuitable for use as carpet backing layers. Coatings for architecturalworks are also contemplated as well as coatings for controlled releasecoatings on fertilizer pellets or as coatings to control surfaceproperties such as coefficient of friction. Additionally somedispersions can be used to prepare stable froths and foams, as describedin “Froths and Durable Foams of Dispersed Olefin Polymers and articlesPrepared from Same” PCT Application Number 2004027593 filed Aug. 25,2004 (Attorney's Docket Number 63,213C).

Some aqueous dispersions described herein are used as a binder in acoating composition for a coated wall paper; a fiber coating agent (forimproving the strength, moisture adsorption, or water repellency of thefiber); a net for construction, a sizing agent for nylon, polyester orglass fibers; a sizing agent/thermal adhesive of a paper or a nonwovenfabric; and an agent for imparting heat sealability with a paper or afilm; a thermal adhesive of a sterilized paper; a binder of an ink or acoating composition; a surface coating agent for a paper or a filmadapted for use with an ink jet printer; an agent for improving chippingresistance of an automotive coating composition; and the like.

In some embodiments, the aqueous dispersions have additional componentsin an amount that does not adversely affect the object of the presentinvention. Exemplary such additional components include water-solubleamino resins such as water-soluble melamine resin and water-solublebenzoguanamine resin and water-soluble epoxy resins for improvingcoating performance; organic thickeners such as polyvinyl alcohol,polyvinyl pyrrolidone, polyvinyl methylether, polyethylene oxide,polyacrylamide, polyacrylic acid, carboxy methyl cellulose, methylcellulose, and hydroxyethyl cellulose and inorganic thickeners such assilicon dioxide, active clay, and bentonite for improving the stabilityand adjusting the viscosity of the dispersion; dispersing agents such asnonionic dispersing agents and anionic dispersing agents andwater-soluble polyvalent metal salts for improving the stability of thedispersion; other additives such as anti-rust agent, anti-mold agent, UVabsorber, thermal stabilizer, foaming agent, antifoaming agent, and thelike; pigments such as titanium white, red iron oxide, phthalocyanine,carbon black, permanent yellow; and fillers such as calcium carbonate,magnesium carbonate, barium carbonate, talk, aluminum hydroxide, calciumsulfate, kaolin, mica, asbestos, mica, and calcium silicate.

EXAMPLES Preparation Example 1

100 parts by weight of a thermoplastic ethylene-vinyl acetatecommercially available from DuPont having a vinyl acetate content ofabout 28 wt %, a density of about 0.95 g/cm3 (ASTM D-792) and a meltindex of about 6 g/10 min. (as determined according to ASTM D1238 at190° C. and 2.16 kg), and a melting point of about 73° C. (as determinedaccording to ASTM D3417) and 4.2 parts by weight of a C₃₂ carboxylicacid (Unicid 425 manufactured by Baker-Petrolite, acid value 97 mgKOH/g) are melt kneaded at 180° C. in twin screw extruder at a rate of8.3 kg/hr.

Upon the melt kneaded resin/surfactant, 4.6 wt % aqueous solution ofpotassium hydroxide is continuously fed into a downstream injection portat a rate 0.9 kg/hr (at a rate of 10 wt % of the total mixture). Thisaqueous dispersion is subsequently diluted with additional water at arate of 5.7 kg/hr before exiting the extruder. An aqueous dispersionhaving a solids content of 56 wt % at pH 10.7 is obtained. The dispersedpolymer phase measured by a Coulter LS230 particle analyzer consisted ofan average volume diameter of 0.56 micron and a particle sizedistribution (dv/dn) of 1.45. The term “dispersed polymer phase” simplyrefers to the thermoplastic resin in the dispersion.

Preparation Example 2

100 parts by weight of a thermoplastic ethylene/1-octene copolymer withan octene content of about 38 wt %, a density of about 0.87 g/cm3 (ASTMD-792) and a melt index of about 5 g/10 min. (as determined according toASTM D1238 at 190° C. and 2.16 kg) a Mw/Mn of about 2.0, and a meltingpoint of about 63° C. (as determined by DSC at a scanning rate of about10° C. per minute), commercially available from DuPont Dow Elastomers,and 3.1 parts by weight of a C18/C16 carboxylic acid (Industrene 106manufactured by CK Witco, acid value 200 mg KOH/g) are melt kneaded at125° C. in twin screw extruder at a rate of 7.9 kg/hr.

Upon the melt kneaded resin/surfactant, 23.9 wt % aqueous solution ofpotassium hydroxide is continuously fed into a downstream injection portat a rate 0.2 kg/hr (at a rate of 2.5 wt % of the total mixture). Thisaqueous dispersion is subsequently diluted with additional water at arate of 5.4 kg/hr before exiting the extruder. To further dilute theresulting dispersion, additional water is added at a rate of 0.7 kg/hrafter the mixture exited the extruder. An aqueous dispersion having asolids content of 56 wt % at pH 9.6 is obtained. The dispersed polymerphase measured by a Coulter LS230 particle analyzer consisted of anaverage volume diameter of 2.04 micron and a particle size distribution(dv/dn) of 1.18.

Preparation Example 3

100 parts by weight of a thermoplastic ethylene/1-octene copolymer withoctene content of about 38 wt %, a density of about 0.87 g/cm3 (ASTMD-792) and a melt index of about 5 g/10 min. (as determined according toASTM D1238 at 190° C. and 2.16 kg) a Mw/Mn of about 2.0, and a meltingpoint of about 63° C. (as determined by DSC at a scanning rate of about10° C. per minute.), commercially available from DuPont Dow Elastomers,and 3.6 parts by weight of a C22/C18 carboxylic acid (High-erucicrapeseed oil manufactured by Montana Specialty Mills, acid value 97 mgKOH/g) are melt kneaded at 150° C. in twin screw extruder at a rate of5.0 kg/hr.

Upon the melt kneaded resin/surfactant, 16.3 wt % aqueous solution ofpotassium hydroxide is continuously fed into a downstream injection portat a rate 0.1 kg/hr (at a rate of 2.0 wt % of the total mixture). Thisaqueous dispersion is subsequently diluted with additional water at arate of 3.2 kg/hr before exiting the extruder. To further dilute theresulting dispersion, additional water is added at a rate of 0.8 kg/hrafter the mixture exited the extruder. An aqueous dispersion having asolids content of 55 wt % at pH 10.7 is obtained. The dispersed polymerphase measured by a Coulter LS230 particle analyzer consisted of anaverage volume diameter of 1.11 micron and a particle size distribution(dv/dn) of 1.85.

Preparation Example 4

100 parts by weight of a thermoplastic ethylene/1-octene copolymer withoctene content of about 38 wt %, a density of about 0.87 g/cm3 (ASTMD-792) and a melt index of about 5 g/10 min. (as determined according toASTM D1238 at 190° C. and 2.16 kg) a Mw/Mn of about 2.0, and a meltingpoint of about 63° C. (as determined by DSC at a scanning rate of about10° C. per minute.), commercially available from DuPont Dow Elastomersand 3.1 parts by weight of a C26 carboxylic acid (Unicid 350manufactured by Baker-Petrolite, acid value 115 mg KOH/g) are meltkneaded at 150° C. in twin screw extruder at a rate of 9.7 kg/hr.

Upon the melt kneaded resin/surfactant, 12.5 wt % aqueous solution ofpotassium hydroxide is continuously fed into a downstream injection portat a rate 0.2 kg/hr (at a rate of 2.0 wt % of the total mixture). Thisaqueous dispersion is subsequently diluted with additional water at arate of 7.5 kg/hr before exiting the extruder. An aqueous dispersionhaving a solids content of 56 wt % at pH 10.8 is obtained. The dispersedpolymer phase measured by a Coulter LS230 particle analyzer consisted ofan average volume diameter of 0.79 micron and a particle sizedistribution (dv/dn) of 1.95.

Preparation Example 5

100 parts by weight of a thermoplastic propylene-ethylene copolymer withan ethylene content of about 12.7 wt %, a density of about 0.864 g/cm3(ASTM D-792) and a melt flow rate of about 23 g/10 min. (as determinedaccording to ASTM D1238 at 230° C. and 2.16 kg), a melting point of60-70° C., a Mw/Mn of about 2.0, and a flexural modulus of about 4 kpsi,and 6.4 parts by weight of a C₂₆ carboxylic acid (Unicid 350manufactured by Baker-Petrolite, acid value 115 mg KOH/g) are meltkneaded at 150° C. in twin screw extruder at a rate of 1.6 kg/hr.

Upon the melt kneaded resin/surfactant, 25 wt. % aqueous solution ofpotassium hydroxide is continuously fed into a downstream injection portat a rate 0.08 kg/hr (at a rate of 4.8 wt % of the total mixture). Thisaqueous dispersion is subsequently diluted with additional water at arate of 1.5 kg/hr before exiting the extruder. An aqueous dispersionhaving a solids content of 51 wt % at pH 11.6 is obtained. The dispersedpolymer phase measured by a Coulter LS230 particle analyzer consisted ofan average volume diameter of 0.61 micron and a particle sizedistribution (dv/dn) of 1.31.

Preparation Example 6

100 parts by weight of a thermoplastic propylene-ethylene copolymer withcomonomer content of about 9 wt %, a melting point of 86° C., a meltflow rate of about 25 g/10 min. (as determined according to ASTM D1238at 230° C. and 2.16 kg), and a Mw/Mn of about 2.0, and 42.9 parts byweight of an ethylene acrylic acid copolymer, available from The DowChemical Company under the tradename PRIMACOR™ 5980i, with a melt indexof about 15 g/10 min determined according to ASTM D1238 at 125° C./2.16kg (which is equivalent to about 300 g/10 min when determined accordingto ASTM D1238 at 190° C./2.16 kg), an acrylic acid content of about 20.5wt. %, and a DSC melting point of about 77° C. are melt kneaded at 170°C. in twin screw extruder at a rate of 4.3 kg/hr.

Upon the melt kneaded resin/surfactant, 11.7 wt. % aqueous solution ofpotassium hydroxide is continuously fed into a downstream injection portat a rate 1.6 kg/hr (at a rate of 27.1 wt % of the total mixture). Thisaqueous dispersion is subsequently diluted with additional water at arate of 2.7 kg/hr before exiting the extruder. To further dilute theresulting dispersion, additional water is added at a rate of 2.3 kg/hrafter the mixture exited the extruder. An aqueous dispersion having asolids content of 41 wt % at pH 9.9 is obtained. The dispersed polymerphase measured by a Coulter LS230 particle analyzer consisted of anaverage volume diameter of 0.86 micron and a particle size distribution(dv/dn) of 1.48.

As demonstrated above, embodiments of the invention provide new methodsfor making a coated substrate by applying and drying dispersions on thesubstrate, and those coated substrates are useful for many applications.In some instances, the new methods make the coatings using dispersionsthat have one or more of the following advantages. First, some newcoatings made from the dispersions have better durability. Certaincoatings made from the dispersions exhibit improved adhesion propertiesand others may have improved adhesion as well as good toughness anddurability. Other coatings made from the dispersions are easier toprocess in a melt-extrusion process. In particular, some coatings madefrom the dispersions are easier to process due to the low melting pointof the polymers deposited from the dispersions. Some coatings made fromthe dispersions have the feature of being low yellowing. Othercharacteristics and additional advantages are apparent to those skilledin the art.

As discussed above, aqueous dispersions made in accordance withembodiments described herein may be particularly useful in creatingcoatings for various substrates. Exemplary substrates include, but arenot limited to, polypropylene, polyethylene terephthalate, polyethylene,other polyolefins, oriented polyolefins, such as biaxially orientedpolypropylene (BOPP), polycarbonate, polyimide, polyamide, polyphenylenesulfide, polysulfone, aromatic polyester, polyether ether ketone,polyether sulfone, and polyether imide.

After drying, the resultant film may be useful in a number ofapplications. FIG. 2 is a flowchart describing one embodiment of thepresent invention. As shown in FIG. 2, the first step in the process isto produce an aqueous polymer dispersion (step 200). The next step (step202) is to coat a substrate with the dispersion. The coated substrate isthen dried to form the final product (step 204). Each of the steps willbe explained in more detail below.

Forming the Dispersion (Step 200)

This step is discussed in detail in the paragraphs above. However, somediscussion is provided below for the sake of clarity. In forming thedispersion, it is important to note that the resin(s) that provide thebasis for the dispersion is a significant element and controls ormodifies at least the following characteristics:

Heat seal behavior—heat seal initiation temperature, seal strength, andhot tack;

Adhesion to base film substrate; and

Film formation characteristics—during the drying of the dispersion, theparticles preferably would coalesce to form a coherent, transparentlayer.

Polymers that may be used in embodiments of the invention includeAFFINITY™ EG 8200 co-polymer (0.870 g/cc, 5 MI) and/or DE 4300.02 apropylene based copolymer (12% ethylene, 25 MFR), both of which areavailable from The Dow Chemical Company, Midland, Mich. Both polymersprovide a low heat seal initiation temperature, good adhesion tosubstrates, and can form a film when dried.

In other embodiments, a copolymer of propylene, ethylene and,optionally, one or more unsaturated comonomers, e.g., C₄₋₂₀ α-olefins,C₄₋₂₀ dienes, vinyl aromatic compounds (e.g., styrene), etc may be used.These copolymers are characterized as comprising at least about 60weight percent (wt %) of units derived from propylene, about 0.1-35 wt %of units derived from ethylene, and 0 to about 35 wt % of units derivedfrom one or more unsaturated comonomers, with the proviso that thecombined weight percent of units derived from ethylene and theunsaturated comonomer does not exceed about 40. These copolymers arealso characterized as having at least one of the following properties:(i) ¹³C NMR peaks corresponding to a regio-error at about 14.6 and about15.7 ppm, the peaks of about equal intensity, (ii) a skewness index,S_(ix), greater than about −1.20, (iii) a DSC curve with a T_(me) thatremains essentially the same and a T_(max) that decreases as the amountof comonomer, i.e., the units derived from ethylene and/or theunsaturated comonomer(s), in the copolymer is increased.

In other embodiments, a copolymer of propylene and one or moreunsaturated comonomers may be used. These copolymers are characterizedin having at least about 60 wt % of the units derived from propylene,and between about 0.1 and 40 wt % the units derived from the unsaturatedcomonomer. These copolymers are also characterized as having at leastone of the following properties: (i) ¹³C NMR peaks corresponding to aregio-error at about 14.6 and about 15.7 ppm, the peaks of about equalintensity, (ii) a skewness index, S_(ix), greater than about −1.20,(iii) a DSC curve with a T_(me) that remains essentially the same and aT_(max) that decreases as the amount of comonomer, i.e., the unitsderived from the unsaturated comonomer(s), in the copolymer isincreased.

In other embodiments, a blend of two or more copolymers, in which atleast one copolymer is at least one of the propylene/ethylene andpropylene/unsaturated comonomer copolymers described above (individuallyand collectively “P/E* copolymer”), may be used. The amount of eachcomponent in the blend can vary to convenience. The blend may containany weight percent, based on the total weight of the blend, of eithercomponent, and the blend may be either homo- or heterophasic. If thelatter, the copolymer of the first or second embodiment of thisinvention can be either the continuous or discontinuous (i.e.,dispersed) phase.

In other embodiments, the invention relates to a blend of (a) at leastone propylene homopolymer, and (b) at least one other polymer, e.g. anEP or EPDM rubber. The propylene homopolymer is characterized as having¹³C NMR peaks corresponding to a regio-error at about 14.6 and about15.7 ppm, the peaks of about equal intensity. Preferably, the propylenehomopolymer is characterized as having substantially isotactic propylenesequences, i.e., the sequences have an isotactic triad (mm) measured by¹³C NMR of greater than about 0.85.

The at least one other polymer of (b) may be a polyolefin such as one ormore of a polyethylene, ethylene/α-olefin, butylene/α-olefin,ethylene/styrene and the like. The blend may contain any weight percent,based on the total weight of the blend, of either component, and theblend may be either homo- or heterophasic. If the latter, the propylenehomopolymer can be either the continuous or dispersed phase.

Methods for forming these types of polymers are disclosed in U.S.Published Patent Application No. 20030204017, which is expresslyincorporated by reference in its entirety.

Further, as discussed in the dispersion section above, a surfactant (ormixture of surfactants) may be used to stabilize the dispersion. Byjudiciously selecting the surfactant or surfactants, it is possible tocontrol or modify at least some of the following characteristics:

Dispersion Particle Size; Film Formation Characteristics;

Shear and shelf stability—the ability of the dispersion to withstandhigh shear (shear stability) and extended time (shelf stability) withouta significant change in dispersion properties (e.g., particle size);

Wettability—the ability to flow onto a substrate without “drawing back”or “beading” on the substrate; and

Adhesion to a substrate.

As noted above, the surfactant may be a single surfactant or a blend ofseveral surfactants. The surfactant selected should be able to initiallydisperse the desired polymer or polymer solution. Selected surfactantsthat are effective for this include long chain fatty acids (C18 throughC32) neutralized via a base (typically NaOH, KOH, and NH₄OH). Oneparticular example of this type is oleic acid neutralized via KOH. Othersurfactants include ethylene-acrylic acid copolymers neutralized via abase. One example is PRIMACOR™ 5980I copolymer (20 wt % acrylic acid,300 MI, available from The Dow Chemical Company, Midland, Mich.)neutralized via KOH. Another group of useful surfactants includessulfonic acid salts. One example is Rhodocal™ DS-10 surfactant(available from Rhodia, Inc. Cranbury, N.J.).

In addition to the surfactant used to initially disperse the polymer,additional surfactants can be added to improve characteristics such aswettability and shear stability. Sulfonic acid salts have proven to beeffective in this capacity.

One specific example of a surfactant package for the polyolefindispersion includes long chain fatty acids from C12 to C60 in an amountfrom 0 to 10% by weight based on polymer, ethylene-acrylic acid (EAA) inan amount from 0 to 50% by weight based on polymer, and sulfonic acidsalts in an amount from 0 to 10% by weight based on polymer, wherein thetotal surfactant loading is less than about 50% by weight based onpolymer. In other embodiments, the total surfactant loading may be lessthan about 10% by weight based on polymer. In other embodiments, thetotal surfactant loading may be less than about 5% based on polymer. Inspecific embodiments, neutralization of the long chain fatty acids andthe EAA is by addition of a base in an amount ranging from 25 to 200% ona molar basis.

In another embodiment, a surfactant package for the polyolefindispersion includes long chain fatty acids from C12 to C40 in an amountfrom 0 to 5% by weight based on polymer, ethylene-acrylic acid in anamount from 0 to 30% by weight based on polymer, and sulfonic acid saltsin an amount from 0 to 5% by weight based on polymer, wherein the totalsurfactant loading is 1.0% by weight based on polymer. In specificembodiments, neutralization of the long chain fatty acids and the EAA isby addition of a base from 50 to 150% on a molar basis.

In another embodiment, a surfactant package for the polyolefindispersion includes long chain fatty acids from C18 to C30 in an amountfrom 2 to 4% by weight based on polymer, and sulfonic acid salts in anamount from 1 to 3% by weight based on polymer. In selected embodiments,neutralization of the long chain fatty acids and the EAA is by additionof a base from 75 to 125% on a molar basis.

Another feature of dispersions in accordance with the invention that maybe controlled in order to provide useful coatings on substrates includescontrolling dispersion particle size. In selected embodiments, theaverage particle size (based on volume fraction) of the dispersion maybe less than 1 micron to achieve a transparent film at the low coatingthicknesses desired (1 to 2 micron dry coating thickness).

However, other particle sizes may be useful depending on the particularapplication selected. In some embodiments, the particle size of thedispersion may be <5 micron. In selected embodiments, the particle sizeof a dispersion may be <2 micron, and, in certain embodiments, theparticle size of a dispersion may be <1 micron.

Another aspect of a dispersion in accordance with the invention that maybe controlled is the solids content. A proper range of solids content ofa dispersion may prevent separation of the dispersed polymer particlesfrom the water and/or reduce the cost of transportation as less wateraccompanies the polymer. In selected embodiments, the solids content ofthe dispersion may be greater than 50% solids by weight. In someembodiments, the solids content of the dispersion is from 10 to 70%solids by weight. In other embodiments, the solids content of thedispersion is from 20 to 60% solids by weight, and in other embodiments,the solids content of the dispersion is from 40 to 55% solids by weight.

Another aspect of dispersions in accordance with the invention that maybe controlled is the shear stability. The process of coating adispersion onto a film substrate at low thickness often requiresexposure of the dispersion to very high shear rates. In preferredembodiments, the dispersion is able to withstand this exposure withoutappreciable coagulation. In certain embodiments, it is desirable to haveless than 0.5 g of polymer coagulate based on a 100 g dispersion sampleexposed to the high shear.

Also, the overall pH of a dispersion may be significant in controllingthe wettability and adhesion of the dispersion onto the desired filmsubstrate. For low surface energy substrates such as biaxially orientedpolypropylene (BOPP), the pH of the dispersion is preferably less than11. In some embodiments, the pH of the dispersion is from 7.5 to 13. Inother embodiments, the pH of the dispersion is from 8 to 12, and inother embodiments, the pH of the dispersion is from 8 to 11.

Coating Application Conditions (Step 202)

After the dispersion has been produced, it is coated on to a substrate.With respect to the coating thickness, the thickness of the appliedcoating is important in controlling the hot tack and seal strength ofthe finished film. A coating thickness of 1 to 2 microns is typicallyneeded to generate a seal strength >200 Ow, which is a suitable strengthfor a packaging application. Preferred thickness for the dried coatingis from 0.5 to 75 microns. In certain embodiments, a coating thicknessfor the dried coating is from 0.5 to 25 microns. In other embodiments, acoating thickness for the dried coating is from 0.75 to 5, or from 0.75to 2, microns.

Typical resins that may be used include the following resins alone andin blends: ethylene homopolymers such as LDPE, ethylene-vinyl compoundssuch as ethylene-vinyl acetate (EVA) and ethylene-methyl acrylate (EMA),ethylene-alpha olefin copolymers such as ethylene-butene,ethylene-hexene, and ethylene-octene copolymers, propylene homopolymers,and propylene copolymers and interpolymers such as propylene-ethylenecopolymers and propylene-ethylene-butene interpolymers.

More preferred polymers as coatings on BOPP and other polyolefinsubstrates include ethylene-octene copolymers having a density between0.85 and 0.90 g/cc and melt index (ASTM D-1238 190° C. with 2.16 kgweight) from 0.1 to 100 g/10 min. Propylene-ethylene copolymers havingan ethylene content between 5 and 20% by weight and a melt flow rate(ASTM D-1238 230° C. with 2.16 kg weight) from 0.5 to 300 g/10 min. Morepreferably polymers as coatings on BOPP and other polyolefin substratesinclude ethylene-octene copolymers having a density between 0.86 and0.88 g/cc and melt index (ASTM D-1238 190° C. with 2.16 kg weight) from0.8 to 35 g/10 min. In other embodiments, propylene-ethylene copolymershaving an ethylene content between 9 and 15% by weight and a melt flowrate (ASTM D-1238 230° C. with 2.16 kg weight) from 1 to 30 g/10 min areused.

Embodiments of the present invention are particularly suited for usewith oriented substrates. “Solid state orientation” herein refers to theorientation process carried out at a temperature higher than the highestTg (glass transition temperature) of resins making up the majority ofthe structure and lower than the highest melting point, of at least someof the film resins, that is at a temperature at which at least some ofthe resins making up the structure are not in the molten state. Solidstate orientation may be contrasted to “melt state orientation” that isincluding hot blown films, in which stretching takes place immediatelyupon emergence of the molten polymer film from the extrusion die.

“Solid state oriented” herein refers to films obtained by eithercoextrusion or extrusion coating of the resins of the different layersto obtain a primary thick sheet or tube (primary tape) that is quicklycooled to a solid state to stop or slow crystallization of the polymers,thereby providing a solid primary film sheet, and then reheating thesolid primary film sheet to the so-called orientation temperature, andthereafter biaxially stretching the reheated film sheet at theorientation process (for example a trapped bubble method) or using asimultaneous or sequential tenter frame process, and finally rapidlycooling the stretched film to provide a heat shrinkable film. In thetrapped bubble solid state orientation process the primary tape isstretched in the transverse direction (TD) by inflation with airpressure to produce a bubble, as well as in the longitudinal direction(LD) by the differential speed between the two sets of nip rolls thatcontain the bubble. In the tenter frame process the sheet or primarytape is stretched in the longitudinal direction by accelerating thesheet forward, while simultaneously or sequentially stretching in thetransverse direction by guiding the heat softened sheet through adiverging geometry frame.

When referring to the average volume diameter of a thermoplastic resinin a dispersion, or a dispersion having an average volume diameterparticle size, one of ordinary skill in the art will recognize thatother materials such as filler may also be present in the dispersedparticles, and would be included in the diameter size. When measuringthe average volume diameter all the dispersed solids are included.

Substrates such as film and film structures particularly benefit fromthe novel coating methods and coating compositions described herein andthose substrates can be made using conventional hot blown filmfabrication techniques or other biaxial orientation processes such astenter frames or double bubble processes. Conventional hot blown filmprocesses are described, for example, in The Encyclopedia of ChemicalTechnology, Kirk-Othmer, Third Edition, John Wiley & amp; Sons, NewYork, 1981, Vol. 16, pp. 416-417 and Vol. 18, pp. 191-192. Biaxialorientation film manufacturing process such as described in a “doublebubble” process as in U.S. Pat. No. 3,456,044 (Pahlke), and theprocesses described in U.S. Pat. No. 4,352,849 (Mueller), U.S. Pat. No.4,597,920 (Golilce), U.S. Pat. No. 4,820,557 (Warren), U.S. Pat. No.4,837,084 (Warren), U.S. Pat. No. 4,865,902 (Golike et al.), U.S. Pat.No. 4,927,708 (Herran et al.), U.S. Pat. No. 4,952,451 (Mueller), U.S.Pat. No. 4,963,419 (Lustig et al.), and U.S. Pat. No. 5,059,481 (Lustiget al.), can also be used to make substrates for coating by the novelcoating methods and coating compositions described herein. The substratefilm structures can also be made as described in a tenter-frametechnique, such as that used for oriented polypropylene.

Other multi-layer film manufacturing techniques for food packagingapplications are described in Packaging Foods With Plastics, by WilmerA. Jenkins and James P. Harrington (1991), pp. 19-27, and in“Coextrusion Basics” by Thomas I. Butler, Film Extrusion Manual:Process, Materials, Properties pp. 31-80 (published by TAPPI Press(1992)).

The substrate films may be monolayer or multilayer films. The substratefilm to be coated can also be coextruded with other layer(s) or the filmcan be laminated onto another layer (s) in a secondary operation to formthe substrate to be coated, such as that described in Packaging FoodsWith Plastics, by Wilmer A. Jenkins and James P. Harrington (1991) orthat described in “Coextrusion For Barrier Packaging” by W. J. Schrenkand C. R. Finch, Society of Plastics Engineers RETEC Proceedings, Jun.15-17 (1981), pp. 211-229. If a monolayer substrate film is produced viatubular film (that is, blown film techniques) or flat die (that is, castfilm) as described by K. R. Osborn and W. A. Jenkins in “Plastic Films,Technology and Packaging Applications” (Technomic Publishing Co., Inc.(1992)), then the film must go through an additional post-extrusion stepof adhesive or extrusion lamination to other packaging material layersto form a multilayer structure to be used as the substrate. If thesubstrate film is a coextrusion of two or more layers (also described byOsborn and Jenkins), the film may still be laminated to additionallayers of packaging materials, depending on the other physicalrequirements of the final film.

“Laminations Vs. Coextrusion” by D. Dumbleton (Converting Magazine(September 1992)), also discusses lamination versus coextrusion.Monolayer and coextruded films can also go through other post extrusiontechniques, such as a biaxial orientation process.

Extrusion coating is yet another technique for producing multilayer filmstructures as substrates to be coated using the novel coating methodsand coating compositions described herein. The novel coatingcompositions comprise at least one layer of the coated film structure.Similar to cast film, extrusion coating is a flat die technique.

The films and film layers of this invention are useful in vertical orhorizontal-form-fill-seal (HFFS or VFFS) applications. Relevant patentsdescribing these applications include U.S. Pat. No. 5,228,531; U.S. Pat.No. 5,360,648; U.S. Pat. No. 5,364,486; U.S. Pat. No. 5,721,025; U.S.Pat. No. 5,879,768; U.S. Pat. No. 5,942,579; U.S. Pat. No. 6,117,465.

Generally for a multilayer film structure, the novel coating methodsapply the coating compositions to the substrate in order to form atleast one layer of the total multilayer film structure. Other layers ofthe multilayer structure may include but are not limited to barrierlayers, and/or tie layers, and/or structural layers.

Various materials can be used for these layers, with some of them beingused as more than one layer in the same film structure. Some of thesematerials include: foil, nylon, ethylene/vinyl alcohol (EVOH)copolymers, polyvinylidene chloride (PVDC), polyethylene terephthalate(PET), polypropylene, oriented polypropylene (OPP), ethylene/vinylacetate (EVA) copolymers, ethylene/acrylic acid (EAA) copolymers,ethylene/methacrylic acid (EMAA) copolymers, LLDPE, HDPE, LDPE, nylon,graft adhesive polymers (for example, maleic anhydride graftedpolyethylene), and paper. Generally, the multilayer film structurescomprise from 2 to 7 layers.

Substrate films can be made by cast extrusion (for monolayer films) orcoextrusion (for multilayer films) by techniques well known in the art.The films can be quenched, irradiated by electron beam irradiation at adosage of between 20 and 35 kiloGrays, and reheated to their orientationtemperature, and then oriented at a ratio of up to 1.5:1, or up to 2:1,or up to 3:1, or up to 4:1, or up to 5:1 in each of the longitudinal(also called machine-direction) and transverse (also calledcross-direction) directions. In one embodiment, the orientation is about5:1 in the traverse direction and about 10:1 in the longitudinaldirection. In another embodiment the orientation is about 7:1 in each ofthe longitudinal and transverse directions.

The substrate films can be made by any suitable process, includingcoextrusion, lamination, extrusion coating, or corona bonding and can bemade by tubular cast coextrusion, such as that shown in U.S. Pat. No.4,551,380 (Schoenberg). Bags made from the film can be made by anysuitable process, such as that shown in U.S. Pat. No. 3,741,253 (Brax etal.). Side or end sealed bags can be made from single wound or doublewound films.

Substrate films can be oriented by any suitable process, including atrapped bubble process or a simultaneous or sequential tenterframeprocess. Films can have any total thickness desired, so long as the filmprovides the desired properties for the particular packaging operationin which the films is used. Final film thicknesses can vary, dependingon process, end use application, etc. Typical thicknesses range from 0.1to 20 mils, preferably 0.2 to 15 mils, more preferably 0.3 to 10 mils,more preferably 0.3 to 5 mils, more preferably 0.3 to 2 mils, such as0.3 to 1 mil.

Suitable thermoplastic polymer materials include, but are not limitedto, polyesters, polycarbonates, polyarylates, polyamides, polyimides,polyamide-imides, polyether-amides, polyetherimides, polyaryl ethers,polyarylether ketones, aliphatic polyketones, polyphenylene sulfide,polysulfones, polystyrenes and their derivatives, polyacrylates,polymethacrylates, cellulose derivatives, polyethylenes, polypropylene(preferably homopolymers), other polyolefins, copolymers having apredominant olefin monomer, fluorinated polymers and copolymers,chlorinated polymers, polyacrylonitrile, polyvinylacetate,polyvinylalcohol, polyethers, ionomeric resins, elastomers, siliconeresins, epoxy resins, and polyurethanes. Miscible or immiscible polymerblends comprising any of the above-named polymers, and copolymerscomprising any of the constituent monomers of any of the above-namedpolymers, are also suitable, provided an oriented film may be producedfrom such a blend or copolymer.

As used herein the term “copolymer” and “interpolymer” are usedinterchangeably, to mean polymers formed from two or more monomers.

While reference to specific thermoplastic resins have been made,embodiments of the present invention may be generally used with anysuitable thermoplastic resin. In addition, while reference has been madeto single layers, it is expressly within the scope of the presentinvention that multiple layers may be used. Thus, combinations of layerssuch as those described herein may be used. In addition, however, it isexpressly within the scope of the present invention that other layerswhich may be formed from other materials may be overlayed or interposedbetween layers formed from the dispersions disclosed herein.

Drying Conditions (Step 204)

Once the dispersion is coated onto the desired substrate, the coating isdried to remove the water and to coalesce the polymer particles into asubstantially continuous film. In one embodiment, an oven may be used toaccelerate the drying process. To properly coalesce the polymerparticles, the coating is preferably allowed to reach a temperatureapproximately 20° C. above the melting point of the polymer from whichthe dispersion is produced. As an example, in the case of a dispersionproduced from AFFINITY™ EG 8200 co-polymer (60° C. melting point asdetermined by DSC at a scanning rate of about 10° C. per minute), thecoated film should reach a temperature of about 80° C.

In selected embodiments, the temperature range used ranges from the peakmelting point of the polymer base of the dispersion to the softeningpoint of the base film. In certain embodiments, the coated substrate mayexit the drying oven at a temperature from 10° C. above the peak meltingpoint of the polymer base of the dispersion to 10° C. below thesoftening point of the base film. In other embodiments the substrate mayexit the drying oven at a temperature from 20° C. above the peak meltingpoint of the polymer base of the dispersion to 20° C. below thesoftening point of the base film.

Example 1

In one embodiment, a sample of AFFINITY™ EG-8200 co-polymer isdispersed, using the method described in U.S. Pat. No. 5,539,021 (Pate),which is hereby incorporated by reference in its entirety, using 4 wt %Rhodacal™ DS-10 surfactant as an emulsifier and toluene as a solvent.After vacuum stripping, the resultant dispersion has an average volumediameter of 0.80 μm at 46.0% solids loading.

An untreated (i.e., no corona treatment) LLDPE film made from DOWLEX™2071 polyethylene (available from The Dow Chemical Company, Midland,Mich.) of 2 mils (50.8 microns) thickness is cut into 12 inch by 6 inchsheets. Each of the sheets is taped to a sheet of glass and coated usingwire-round rods (rod #'s 4, 12, 20, and 28). Table 1 below and FIG. 3show the coat weights of the various samples.

TABLE 1 Coating Weight and Thickness of Dispersion Coated LDPE FilmSamples Coat Coat Gross Wt. Std Dev. Coat Wt. Thickness Thickness Rod#g/m² g/m² g/m² mils μm Control 45.18 2.22 0.00 0.00 0.00 4 49.00 1.163.82 0.17 4.32 12 57.91 1.41 12.74 0.58 14.73 20 67.19 4.69 22.02 1.0025.40 28 72.01 3.12 26.83 1.21 30.73

For each coated weight, individual strips (1 inch wide) having nobacking are heat sealed at 45, 50, 55, 60, 65, 70, 75, and 80° C.,respectively, using a Packforsk Hot Tack Tester set at 40 psi sealpressure and 0.5 second dwell time. Sealed samples are allowed toequilibrate for at least a day in a room set at 70° F. (21.1° C.) and50% relative humidity before being pulled on Instron model 4501 tensiletesting device. For this experiment, a seal is declared a “weld” if theseal force is greater than the force (4 lbs (1.8 kg)) required toirreversibly elongate and re-orient the crystal structure within the 2mls (50.8 microns) thick LLDPE films. Results of the experiment areshown below in Table 2 and FIG. 4.

As used herein, the temperature at which a seal strength of 0.5 lb/in isachieved is known as the heat seal initiation temperature. The heat sealinitiation temperature for the coatings in this example set is from 45°C. to 60° C., depending on the coating weight.

TABLE 2 Peel Strength for Ethylene-Octene Copolymer Dispersion CoatedLDPE Films Seal Temp, ° C. Mean Peak Peel Strength, lb/in 45 0.075 0.0200.098 0.118 50 0.178 0.201 0.380 0.554 55 0.463 0.530 0.352 1.365 601.048 1.477 2.124 3.456 65 1.144 2.267 3.755 3.196 70 1.155 3.2043.510 >4 75 1.129 3.081 3.815 >4 80 — 1.439 >4 >4 Coating Wt, g/m² 3.8212.7 22.0 26.8

The metric equivalents for the above table is provided below:

Peel Strength for Ethylene-Octene Copolymer Dispersion Coated LDPE FilmsSeal Temp, ° C. Mean Peak Peel Strength, g/cm 45 13 4 18 21 50 32 36 6899 55 83 95 63 244 60 187 264 380 618 65 204 405 671 571 70 206 573627 >700 75 202 551 682 >700 80 — 257 >700 >700 Coating Wt., g/m² 3.8212.7 22.0 26.8

Example 2

A sample of propylene-ethylene co-polymer (ethylene content of 12% byweight with a melt flow rate of about 25 g/10 min as determinedaccording to ASTM D1238 at 230° C. with a 2.16 kg weight) is convertedto an aqueous dispersion using a technique as described in co-pendingU.S. application Ser. No. 10/925,693. 100 parts by weight of thepropylene-ethylene co-polymer and 3.1 parts by weight of a C26carboxylic acid (Unicid 350 manufactured by Baker-Petrolite, acid value115 mg KOH/g) is melt kneaded at 150° C. in twin screw extruder at arate of 6.6 kg/hr.

To the melt kneaded resin/surfactant blend, a 13.5 wt % aqueous solutionof potassium hydroxide is continuously fed into a downstream injectionport at a rate 0.17 kg/hr (which equates to 2.5 wt % of the totalmixture). This aqueous dispersion is subsequently diluted in a two stepprocess with water containing 5.0 wt % dioctyl sodium sulfosuccinate(Aerosol OT-100 manufactured by Cytec Industries) at a rate of 3.7kg/hr, and secondly additional water added at a rate of 1.1 kg/hr beforeexiting the extruder. To further dilute the resulting dispersion,additional water is added at a rate of 1.8 kg/hr after the mixtureexited the extruder. An aqueous dispersion having a solids content of 51wt % at pH 10.2 is obtained. The dispersed polymer phase measured by aCoulter LS230 particle analyzer consisted of an average volume diameterof 0.64 micron and a particle size distribution (dv/dn) of 1.33.

While the polymers discussed here provide good low temperature heat sealinitiation properties, other polymers may also be included in thedispersion to improve other properties. For example, a very low or ultralow density polyethylene, a linear low density polyethylene or highdensity polyethylene could be included in the dispersion to improveother properties. If the oriented substrate is nylon, it may beadvantageous to include a functionalized polymer such as ethyleneacrylic acid or a maleic anyhydride grafted polypropylene. Similarly, ifthe oriented substrate is polyester, other functionalized polymers suchas ethylene vinyl acetate copolymers or ethylene ethyl acrylatecopolymers may be advantageous to include in the dispersion.

A corona treated BOPP (BICOR LBW made by Mobil Chemical Corporation) of1.2 mils is cut into 12 inch by 14 inch sheets. Each of the sheets istaped to a flat foamed plastic board and the dispersion described aboveis coated onto the BOPP (the side without a slip additive) usingwire-round rods (rod #'s 4, 12, and 18). The purpose of the foamedplastic board is to achieve a more consistent coating thickness.

Coated sheets are placed into a convection oven at 135° C. for 5 minutesto dry the dispersion coating. The resulting coating thickness isdetermined gravimetrically. Ten pieces (1-inch by 1-inch) of coated filmsamples are weighed individually and the coating thickness is determinedby subtracting the weight of the base BOPP substrate. A density of 0.864g/cc is used for calculating the coating thickness based on the weightdifference.

TABLE 3 Coating Weight and Thickness of Dispersion Coated BOPP FilmSamples Coat Coat Gross Wt. Std Dev. Coat Wt. Thickness Thickness Rod#g/m² g/m² g/m² mils μm Control 27.75 2.84 0.00 0.00 0.00 4 30.85 2.363.10 0.14 3.59 12 40.46 1.54 12.71 0.58 14.71 18 45.57 2.75 17.83 0.8120.64

For each coated weight, individual strips (1 inch wide) having nobacking are heat sealed from 50 to 140° C. in 10° C. increments, using aPackforsk Hot Tack Tester set at 40 psi seal pressure and 0.5 seconddwell time. Sealed samples are allowed to equilibrate for at least a dayin an ASTM room set at 70° F. (21.1° C.) and 50% relative humiditybefore being pulled on Instron model 4501 tensile testing device at arate of 10 inches per minute. Results of the experiment are shown below.

As used herein, the temperature at which a seal strength of 0.5 lb/in isachieved is defined as the heat seal initiation temperature. The heatseal initiation temperature for the coatings in this example set is fromapproximately 56° C. to 76° C., depending on the coating weight.

TABLE 4 Peel Strength for Propylene-Ethylene Copolymer Dispersion CoatedBOPP Films Seal Temp, ° C. Mean Peak Peel Strength, lb/in 50 0.000 0.3080.000 60 0.000 0.768 0.152 70 0.228 2.290 0.618 80 0.626 2.524 2.083 900.840 2.322 2.200 100 0.878 2.332 2.502 120 0.784 1.980 2.814 130 0.9222.272 2.758 140 0.933 2.580 2.840 Coating Wt., g/m² 3.59 14.71 20.64

Metric equivalents of the above table are provided below:

Peel Strength for Propylene-Ethylene Copolymer Dispersion Coated BOPPFilms Seal Temp, ° C. Mean Peak Peel Strength, g/cm 50 0 55 0 60 0 13727 70 41 409 110 80 112 451 372 90 150 415 393 100 157 417 447 120 140354 503 130 165 406 493 140 167 461 508 Coating Wt., g/m² 3.59 14.7120.64

Thus, dispersions in accordance with embodiments of the presentinvention may be used to coat substrates. In particular, embodiments ofthe present invention provide a film (obtained from the coatedsubstrate), which may have a heat seal initiation temperature of betweenabout 45° C. and 90° C. In other embodiments the heat seal initiationtemperatures may range from 65° C. to 80° C., 70° C. to 75° C., or 70°C. to 80° C. Those of ordinary skill in the art will recognize thatother values within the range may be included.

In selected embodiments, the propylene copolymer may be selected todeliver the desired performance properties. For example, the heat sealinitiation temperature and the heat seal range will be a function of thepropylene copolymer selected. Copolymers with higher comonomer contentwill generally have lower heat seal initiation temperatures.

Those of ordinary skill in the art will also recognize that embodimentsof the present invention may be applied in a non-uniform, or localizedmanner depending on the application. For example, a coating may beapplied only to a portion (e.g., a strip or band at one end) of asubstrate that is needed to be sealed.

While the polymers discussed here provide good low temperature heat sealinitiation properties, other polymers may also be included in thedispersion to improve other properties. For example, a small amount of ahomopolymer polypropylene or a random copolymer polypropylene may beadded to the dispersion to improve heat resistance or to extend hot tackstrength at higher temperatures. If the oriented substrate is nylon, itmay be advantageous to include a functionalized polymer such as ethyleneacrylic acid or a maleic anyhydride grafted polypropylene. Similarly, ifthe oriented substrate is polyester, other functionalized polymers suchas ethylene vinyl acetate copolymers or ethylene ethyl acrylatecopolymers may be advantageous to include in the dispersion.

Advantageously, one or more embodiments of the present invention,provide heat sealable films that may allow for higher packaging linespeeds (due to lower heat seal initiation temperatures), provide theability to seal packages over broad operating windows, and provide goodpackage integrity.

In other words, one or more embodiments of the present invention providethe ability to seal packages over a broad operating window. Duringstartup and shutdown of packaging lines, the temperature of the sealingequipment can often deviate, sometimes by a large amount, from thesetpoint. With a packaging film having a low heat seal initiationtemperature, an adequate seal can still be generated if the sealingequipment is somewhat cooler than desired.

While the invention has been described with respect to a limited numberof embodiments, the specific features of one embodiment should not beattributed to other embodiments of the invention. No single embodimentis representative of all aspects of the inventions. Moreover, variationsand modifications therefrom exist. For example, the dispersionsdescribed herein may comprise other components. Various additives mayalso be used to further enhance one or more properties. In someembodiments, the dispersions are substantially free of any additive notspecifically enumerated herein. Some embodiments of the dispersionsdescribed herein consist of or consist essentially of the enumeratedcomponents. In addition, some embodiments of the methods describedherein consist of or consist essentially of the enumerated steps. Theappended claims intend to cover all such variations and modifications asfalling within the scope of the invention.

1. A coating composition comprising: an aqueous dispersion comprising(A) at least one thermoplastic resin, wherein the thermoplastic resincomprises one or more ethylene-acrylic acid copolymers, one or moreethylene-methacrylic acid copolymers, or combinations thereof; (B)optionally, one or more dispersing agents; (C) one or stabilizingagents; (D) water; wherein the aqueous dispersion has a pH in the rangeof 8 to 11.